It was Mr. Rouhani’s second major speech this week at the United Nations, where he has been engaged in a near-breathless series of appearances and interviews with the Western news media. He appears to want to send the message that he is a reasonable, practical leader who differs from his bombastic predecessor, Mahmoud Ahmadinejad, and who wants urgently to solve Iran’s protracted disputes with the West, most notably the nuclear issue.

Israel, which regards Iran as an existential threat, has repeatedly warned that it may take military action to strike at Iran’s uranium enrichment centers and other nuclear facilities that the Israelis say are part of an Iranian scheme to build a weapon.

The Iranians have frequently pointed out that they have publicly renounced nuclear arms and that — unlike Israel — Iran is a member of the International Atomic Energy Agency, the United Nations nuclear monitor. The Iranians also have countered that Israel is believed to already have an arsenal of nuclear weapons, which it refuses to confirm or deny.

According to the Arms Control Association, a nonproliferation group in Washington,Israel is suspected of having 100 to 200 nuclear warheads. Israel has said it will “not be the first country to introduce nuclear weapons in the Middle East.”

Mr. Rouhani said in his speech on Thursday that the total elimination of nuclear weapons should be the goal, particularly in his part of the world.

“Almost four decades of international efforts to establish a nuclear-weapon-free zone in the Middle East have regrettably failed,” Mr. Rouhani said in a translated version of his speech, furnished by Iran’s United Nations Mission.

“Urgent practical steps toward the establishment of such a zone are necessary,” he said. “Israel, the only nonparty to the nonproliferation treaty in this region, should join thereto without any further delay. Accordingly, all nuclear activities in the region should be subject to the I.A.E.A. comprehensive safeguards.”

Mr. Rouhani said nothing about Iran’s own dispute with the I.A.E.A., which wants access to some restricted military sites in the country to verify that Iran’s nuclear intentions are benign. He also made no reference to Iran’s stalled negotiations with the so-called P5-plus-one countries, the permanent members of the Security Council — Britain, China, France, Russia and the United States — plus Germany, on the larger dispute over uranium enrichment.

He said in the speech that the establishment of a nuclear-free zone in the Middle East would “constitute a contribution to the objective of nuclear disarmament” and called for a conference to establish such a zone, “without any further delay, with the participation of all countries in the region to avoid unwanted consequences.”

Mr. Rouhani commended Secretary General Ban Ki-moon for convening the conference. “No nation should possess nuclear weapons; since there are no right hands for these wrong weapons, as you, Mr. Secretary General, have rightly put it,” he said.

Israel has taken the leading role among foreign countries in aiding and advising Kenyan forces after al-Shabaab Islamist extremists attacked the Westgate shopping mall in Nairobi, according to security and intelligence sources.

A host of other countries have also offered help, including Britain, which has resident MI6 officers in Kenya and special forces training their counterparts in the country.

Metropolitan police anti-terrorist officers are in Kenya to try to monitor the activities of suspects including Samantha Lewthwaite, the widow of the 7/7 London suicide bomber Germaine Lindsay.

The CIA also has officers in Kenya. However, counter-terrorist officials pointed to Israel as the country that has built up extremely close security co-operation as well as commercial ties with Kenya over more than a decade.

Israeli officials kept a public silence about possible involvement in the mall standoff. However, a defence ministry official told the Guardian that a team from Israel's elite counter-terrorism unit had assisted the Kenyan authorities in handling the hostage crisis.

An Israeli border police unit known as Yamam is specially trained in civilian hostage rescue operations.

An Israeli army spokeswoman responded to questions on Israeli involvement with a formula previously used with reference to covert Israeli activities, such as recent air strikes in Syria. "We don't comment on foreign reports," she said.

Reuters news agency quoted an Israeli security source as saying Israeli advisers were helping Kenya with the "negotiating strategy" to help end the siege.

"There are Israeli advisers helping with the negotiating strategy, but no Israelis involved in any imminent storming operation," said the source, who asked not to be identified.

The Israeli foreign ministry said later four of its nationals were in the mall at the time of the attack, and that two fled while two others were rescued. One was lightly wounded, treated and released. The upmarket Westgate shopping complex is part Israeli-owned.

In London on Monday, the defence secretary, Philip Hammond, chaired a meeting of the government's Cobra emergencies committee, as David Cameron cut short a visit to Balmoral to chair a second meeting later in the day.

Downing Street said the prime minister – who has spoken to the Kenyan president, Uhuru Kenyatta – offered help in terms of "policing, intelligence collaboration and other related kinds" of assistance.

UK staff from Addis Ababa in Ethiopia travelled to assist local officials with the efforts in Nairobi and a rapid deployment team was sent from London, the Foreign Office said.

There was no confirmation of any Britons being among those who carried out or planned the Kenya attack, though UK-based individuals, at one time estimated to number 50, have gone to Somalia to join al-Shabaab, the terror group believed to be behind the atrocity.

Intelligence sources said it was clear the attack had been carefully planned over a long period with the help of a network of al-Shabaab sympathisers in Kenya.

The Labour leader, Ed Miliband, offered his support to the government and said: "Those who carried out this attack will be condemned across the globe. The cold-blooded killing of innocent women, children and men is as despicable as it is shocking."

Jerusalem urged the world on Thursday not to be fooled by Iranian President Hassan Rouhani’s smiles and to intensify sanctions against the regime until he takes concrete steps toward dismantling Tehran’s nuclear program.

“One should not be taken in by Rouhani’s deceptive words,” the Prime Minister’s Office said in a statement. “The same Rouhani boasted in the past how he deceived the international community with nuclear talks, even as Iran was continuing with its nuclear program.”

The Prime Minister’s Office comments followed the Iranian president’s two-part interview with NBC on Wednesday and Thursday that aired just before he is to fly to the US and address the UN General Assembly.

Rouhani said Iran was not seeking war, and slammed Israel for bringing “instability” to the Middle East and for questioning his government’s intentions toward nuclear arms.

He called Israel “an occupier, a usurper government that does injustice to the people of the region,” and said it “has brought instability to the region with its war-mongering policies.”

The Prime Minister’s Office ridiculed Rouhani for accusing Israel of causing instability in the region at a time when Iran was sending people into Syria to slaughter innocent civilians, and was supporting terrorism around the world.

Rouhani said during the first part of the interview that Iran would never develop nuclear weapons and that he had “complete authority” to negotiate a nuclear deal with the United States and other Western powers.

The Iranian leader, who took office in August, reiterated that stance when asked about recent comments by Prime Minister Binyamin Netanyahu questioning his motives and calling him a “wolf in sheep’s clothing.”

“We have clearly stated that we are not in pursuit of nuclear weapons and will not be,” Rouhani told NBC.

The Prime Minister’s Office dismissed this as “spin” designed to ensure that the “centrifuges continue to spin,” and said the International Atomic Energy Agency had determined otherwise.

“Only a combination of stopping uranium enrichment, removing all enriched uranium, dismantling the nuclear facility at Qom and stopping the plutonium track will constitute a real halt to the nuclear program,” the PMO said.

“Until these four steps are taken, the international community needs to intensify the pressure on Iran.

“The test is not Rouhani’s words, but rather the Iranian regime’s actions. Even while Rouhani was being interviewed, Iran was moving forward energetically with its nuclear program,” it said.

Rouhani’s regime is trying to cut a deal with the international community whereby it will give up an insignificant part of its nuclear program but retain and further fortify its ability to quickly develop nuclear arms at a time of its choosing, the Prime Minister’s Office said.

According to one Israeli official, Rouhani was long on smiles but short on substance during the interview, not saying yes or no when asked whether Israel should be wiped off the map, and not responding directly when asked whether, like his predecessor Mahmoud Ahmadinejad, he believed the Holocaust was a myth. Asked about the Holocaust directly, Rouhani replied, “What is important to Iran is that countries, people in the region grow closer and prevent aggression and injustice.”

The Prime Minister’s Office responded to his comment on the Holocaust saying “one doesn’t need to be a historian to recognize the existence of the Holocaust, one need only be human.”

The interview was the latest of moves by Rouhani – which included a recent letter exchange with US President Barack Obama – aimed at improving relations with the West.

The White House said on Thursday that the president is open to direct talks between Iran and the US, but only if Tehran is serious about getting rid of its nuclear weapons program.

White House spokesman Jay Carney told reporters that Rouhani delivered some positive- sounding rhetoric in the NBC interview but “actions are more important than words.”

When Obama first ran for president in 2008, he said he would hold direct negotiations with Iran under certain conditions.

Carney said Obama still holds that position.

Obama, according to Carney, would be willing to have bilateral negotiations provided the Iranians were serious about addressing the international community’s insistence that Tehran give up its nuclear weapons program.

“That is the position we hold today,” Carney said.

With both Rouhani and Obama attending the UN General Assembly next week, speculation has grown that the two leaders might have an encounter of some type. Carney said no meeting is scheduled.

It would be a significant contact – no American president has met a top Iranian leader since the 1979 overthrow of the shah and the taking of American hostages at the US Embassy in Tehran.

Reuters contributed to this report.

By Fredrik Dahl

VIENNA | Tue Sep 17, 2013 2:33pm EDT

JERUSALEM | Tue Sep 17, 2013 9:38am EDT

By JODI RUDOREN

Published: September 11, 2013

Deliberate neutrality and ambiguity have thus far governed Israel’s reaction to the Syrian civil war, but America’s deliberations over whether to strike Assad have revealed its true stance.

“We take no part in Syria’s civil war; but if attacked, we’ll react, and react fiercely,” said Israeli Prime Minister Benjamin Netanyahu in the wake of the gas attacks.

Israel has, however, intervened in Syria. The Jewish state deployed strikes in July against Syrian missile convoys destined for one its principal enemies on its northern border, the Lebanese-based Hezbollah.

 Netanyahu and his administration have remained mum on their four unilateral missile attacks since Syria fractured into civil war. The oft-quoted line from the film The Good, the Bad, and the Ugly neatly encapsulates Israel’s approach: “When you have to shoot, shoot. Don’t talk.”

This helps explain the kind of unusual discipline that Netanyahu expects from his cabinet to avoid leaks about strategy regarding Syria and the U.S. response. Public announcements have been limited to Netanyahu and his defense establishment, a surprising restriction for a typically fairly open cabinet.

The Syrian crisis is palpable in Israel, to the degree that people are risking their positions to proclaim the seriousness of the situation. It reached a breaking point when the right-wing housing minister, Uri Ariel, deviated from Netanyahu’s gag order. Perceiving President Obama as dithering on action in Syria, he told Army Radio that “one doesn’t need to wait for tens of thousands more to die in order to intervene.” Netanyahu charged Ariel with endangering Israel’s “national security.”

The savagery of Assad’s alleged multiple deployments of chemical weapons against his own people sent shock waves through Israel. If he’s willing to use deadly nerve agents against his own population, the thinking there goes, what would prevent him from poisoning Israelis that live in a country he has declared at war with Syria? Demand at gas-mask distribution centers increased fourfold in the aftermath of the attack.

Then there is the question of U.S. military strikes. Will any counterattack plan from the Assad regime include an attack on Israel?

The lack of retaliation to the four Israeli breaches of Syrian airspace suggests a low-risk proposition that Assad would issue an order to launch missiles at Israel. It is worth recalling that, in the absence of full-blown war, Assad took no action in 2007 after Israel bombed a nuclear power installation in northeastern Syria.

Predicting outcomes in the Middle East is risky: The astonishingly fast-moving events in the region could dramatically change the calculus. One high-ranking Syrian official declared, “If Damascus is attacked, Tel Aviv will burn.” At the same time, a leading Israeli defense expert Michael Herzog, an international fellow at The Washington Institute for Near East Policy, wrote, “a major Syrian military response against Israel is unlikely” using Israeli assessments of the situation. Netanyahu has voiced a similar prognosis, saying there is “low probability that Israel will become involved in what is happening in Syria.”

Should Israel find a reason to respond, it will most likely be because of attacks from the Shi’ite militia Hezbollah, Assad’s main life-support system (in addition to Iran). According to the Saudi media outlet Okaz, Hezbollah will strike Israel“after receiving a specific order [to do so] from Iran.” The Hezbollah-affiliated press has reported the deployment of combatants from Lebanon to Syria ahead of potential U.S. strikes, and some estimates show between 1,500 - 10,000 Hezbollah fighters already in Syria.

There have even been reports that Hezbollah plans to attack Israel from Syrian territory to avoid damage to Lebanon. Given Hezbollah’s arsenal of as many as100,000 rockets in its southern Lebanon base, Israel’s defense forces have deployed a missile interception system in several cities, counting on Iron Dome anti-rocket batteries and the Patriot and Arrow 3 anti-ballistic missile batteries to protect civilians. For the first-time in Jerusalem’s history, an operational missile defense system was positioned.  

 A limited numbers of reservists have also been called to duty in preparation for attack.

Israel has told the Lebanese government time and again that it will be held accountable for Hezbollah attacks on Israel, but Hezbollah is the de factokingmaker of Lebanese coalition politics. The enormously complex chess game unfolding in the region could mean that Israel may target both Lebanon and Syria if Hezbollah engages in warfare with the Jewish state.

But then, Israel may not need to target anyone. Both Assad and Hezbollah are stumbling, and a new battle with Israel will almost certainly diminish their military ability. Israel may not be required to talk or shoot if they sit back and allow Assad and his backers to attempt to fight with increasingly depleted supplies.                 

Israeli soldiers conducted a military exercise in the Israeli-annexed Golan Heights, near the border with Syria.

JERUSALEM — President Obama’s position on Syria — punish President Bashar al-Assad for using chemical weapons without seeking to force him from power — has been called “half-pregnant” by critics at home and abroad who prefer a more decisive American intervention to end Syria’s civil war.

Israeli officials have consistently made the case that enforcing Mr. Obama’s narrow “red line” on Syria is essential to halting the nuclear ambitions of Israel’s archenemy, Iran. More quietly, Israelis have increasingly argued that the best outcome for Syria’s two-and-a-half-year-old civil war, at least for the moment, is no outcome.

For Jerusalem, the status quo, horrific as it may be from a humanitarian perspective, seems preferable to either a victory by Mr. Assad’s government and his Iranian backers or a strengthening of rebel groups, increasingly dominated by Sunni jihadis.

“This is a playoff situation in which you need both teams to lose, but at least you don’t want one to win — we’ll settle for a tie,” said Alon Pinkas, a former Israeli consul general in New York. “Let them both bleed, hemorrhage to death: that’s the strategic thinking here. As long as this lingers, there’s no real threat from Syria.”

The synergy between the Israeli and American positions, while not explicitly articulated by the leaders of either country, could be a critical source of support as Mr. Obama seeks Congressional approval for surgical strikes in Syria. Some Republicans have pushed him to intervene more assertively to tip the balance in the Syrian conflict, while other politicians from both parties are loath to involve the United States in another Middle Eastern conflict on any terms.

But Israel’s national security concerns have broad, bipartisan support in Washington, and the American Israel Public Affairs Committee, the influential pro-Israel lobby in Washington, weighed in Tuesday in support of Mr. Obama’s approach. The group’s statement said nothing, however, about the preferred outcome of the civil war, instead saying that America must “send a forceful message” to Iran and Hezbollah and “take a firm stand that the world’s most dangerous regimes cannot obtain and use the most dangerous weapons.”

After years of upheaval in the Middle East and tension between Mr. Obama and Prime Minister Benjamin Netanyahu of Israel, the two leaders are now largely in sync on how to handle not just Syria, but also Egypt. Mr. Obama has not withheld American aid to Egypt after the military-backed ouster of the elected Islamist government, while Israel strongly backs the Egyptian military as a source of stability.

On Syria, in fact, Israel pioneered the kind of limited strike Mr. Obama is now proposing: four times this year, it has bombed convoys of advanced weapons it suspected were being transferred to Hezbollah, the Lebanese Shiite militia that Israel considers a major threat.

It has otherwise been content to watch the current stalemate in Syria pull in what it considers a range of enemies: not only the Syrian Army and Iran, but also Hezbollah, which has thousands of fighters engaged on the battlefronts in Syria, and Sunni Islamists aligned against them.

Though Syria and Israel have technically been at war for more than 40 years, the conflict in Syria is now viewed mainly through the prism of Iran. A prolonged conflict is perceived as hurting Iran, which finances Mr. Assad’s war effort. Whether Mr. Obama follows through on his promise to retaliate for the use of chemical weapons is a test of his commitment, ultimately, to prevent an Iranian nuclear bomb — as long as the retaliation does not become a full-scale intervention in Syria.

“If it’s Iran-first policy, then any diversion to Syria is not fruitful,” said Aluf Benn, editor of the Israeli newspaper Haaretz. “From the Israeli point of view, the worst scenario is mission-creep in Syria and America gets entangled in a third war in the Middle East, which paralyzes its ability to strike Iran and limits Israel’s ability to strike Iran as well.”

This spring, when an Israeli official called for an international response to what he said were earlier Syrian chemical attacks, he was muzzled and reprimanded for appearing to pressure the White House. Now, said Eyal Zisser, a historian at Tel Aviv University who specializes in the region, “it’s clear that Israel does not want to appear as somebody that is pushing the United States for a deep involvement.”

There are significant differences between Israel and the United States on Syria. There was widespread criticism here of Mr. Obama’s decision to delay responding to the chemical attack, with the quote “When you have to shoot, shoot, don’t talk” from “The Good, the Bad and the Ugly” becoming a common refrain. One Israeli dentist even took out a large newspaper ad promoting his implant services with a picture of Mr. Obama captioned, “He doesn’t have teeth?”

There has also been a broader debate about how best to respond to the war in Syria.

When the uprising began, many here saw Mr. Assad, who like his predecessor and father had maintained quiet on the border, as “the devil you know,” and therefore preferable to the rebels, some of whom were aligned with Al Qaeda or Sunni militants like the Palestinian Hamas faction.

As the death toll has mounted, more Israelis joined a camp led by Amos Yadlin, a former head of Israeli military intelligence, who argues that the devil you know is, actually, a devil who should be ousted sooner rather than later.

That split remains. But as hopes have dimmed for the emergence of a moderate, secular rebel force that might forge democratic change and even constructive dialogue with Israel, a third approach has gained traction: Let the bad guys burn themselves out.

“The perpetuation of the conflict is absolutely serving Israel’s interest,” said Nathan Thrall, a Jerusalem-based analyst for the International Crisis Group.

Tamara Cofman Wittes, director of the Saban Center for Middle East Policy at the Brookings Institution, was one of several experts who said this view differs from the callous “let them all kill each other” shrug popular here during the long-running Iran-Iraq war. Rather, Ms. Wittes said, the reasoning behind a strike that would not significantly change the Syrian landscape is that the West needs more time to prop up opposition forces it finds more palatable and prepare them for future governing.

She cited dangers for Israel if the conflict continues to drag on, including more efforts to transfer advanced weapons to Hezbollah, instability in Lebanon and pressure on Jordan.

Despite those threats, Matthew Levitt, who studies the region at the Washington Institute for Near East Policy, said Jerusalem and Washington essentially agree that “right now, there’s no good way for this war to end.”

Israeli leaders “want Assad to be punished; they’d like it to be punishing enough that it actually makes a difference in the war but not so much that it completely takes him out,” Mr. Levitt said. “The Israelis do not think the status quo is tenable either, but they think the status quo right now is better than the war ending tomorrow, because the war ending tomorrow could be much worse. There’s got to be a tomorrow, day-after plan.”