WASHINGTON -- The US Senate sent a united message of "grave concern" to US President Barack Obama on Thursday regarding the formation of a reconciliation government between Fatah and Hamas, and what the move might require of Congress in determining future US aid to the Palestinians.

88 senators from across party lines signed the letter sent to the White House, written by Senators Ben Cardin (D-MD) and Susan Collins (R-ME), which warns the new PA unity effort might "jeopardize direct negotiations with Israel to achieve a two-state solution."

"The recent formation of a Palestinian Authority unity government supported by Hamas, a designated Foreign Terrorist Organization that has never publicly accepted the Quartet principles, represents a serious setback to efforts to achieve peace," the senators wrote.

Citing recent appropriations law, which calls for an end to assistance to the PA should Hamas share power in the government or exert "undue influence" over its government, the Senate said the law is clear and warned the president that the chamber would reconsider future aid.

"Any assistance should only be provided when we have confidence that this new government is in full compliance with the restrictions contained in current law," the letter reads.

The State Department considers the current government an interim body, occupied by technocrats unaffiliated with either Palestinian party. Given those circumstances, the Obama administration plans on monitoring the political developments while continuing aid, officials say.

The American Israel Public Affairs Committee, which helped circulate the letter through the halls of the Senate, "commended" the bipartisan group in a statement. They have publicly called for a debate on Capitol Hill on the continuation of aid to the PA.