Secretary of State Rex Tillerson Rex Wayne TillersonGary Cohn: 'I haven't made up my mind' on vote for president in November Kushner says 'Alice in Wonderland' describes Trump presidency: Woodward book Conspicuous by their absence from the Republican Convention MORE acknowledged on Wednesday that he has seen "elements" of President Trump Donald John TrumpObama calls on Senate not to fill Ginsburg's vacancy until after election Planned Parenthood: 'The fate of our rights' depends on Ginsburg replacement Progressive group to spend M in ad campaign on Supreme Court vacancy MORE's plan for peace in the Middle East, and that the proposal is "fairly well-advanced."

Speaking at a press conference in Amman, Jordan, Tillerson declined to provide a time frame for when the proposal might be unveiled, but said that it has been under development for several months.

"I think it’ll be up to the president to decide when he feels it’s time and he’s ready to put that plan forward," Tillerson said. "I will say it’s fairly well advanced, is what I would say."

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Tillerson's comments came moments after he signed a memorandum of understanding alongside Jordanian Foreign Minister Ayman Safadi setting aside $6.4 billion in aid for Jordan, a key Middle East ally for Washington, over the next five years.

Trump has vowed to broker a lasting peace between the Israelis and Palestinians — an effort that he has called the "ultimate deal."

Early on in his presidency, Trump put his son-in-law and senior adviser Jared Kushner Jared Corey KushnerAbraham Accords: New hope for peace in Middle East Tenants in Kushner building file lawsuit alleging dangerous living conditions Trump hosts Israel, UAE, Bahrain for historic signing MORE on the initiative. But the details of such a proposal have remained a closely guarded secret in the White House, and it's unclear when the administration might roll out its plan.

The White House is likely to face complications with any proposal, particularly after Trump announced in December that Washington would recognize Jerusalem as the capital of Israel, a move that reversed decades of U.S. policy.

Jerusalem is revered by Muslims, Christians and Jews, and is considered by Israelis to be their eternal capital. Palestinians, however, have long aspired to establish east Jerusalem as the capital of a future Palestinian state.

Since Trump's announcement, however, Palestinian officials have rejected any U.S. role in peace talks with Israel, arguing that Washington is no longer capable of acting as a fair broker.