As Palestinian president Mahmud Abbas prepares to touch down in Washington for a meeting on Monday with Barack Obama, an extension of peace talks with Israel looks far from certain.
Palestinian and Israeli leaders have been locked in talks US Secretary of State John Kerry fought hard to launch in July after a three-year hiatus, but as negotiations have faltered, Israel has kicked up more obstacles to a peace deal that would end decades of conflict.
Kerry hopes the two sides will agree on a US-proposed framework to guide final status negotiations, before the impending deadline for the current round of talks on April 29.
But he is aware of the danger posed to talks by a recently-concocted Israeli demand -- that Palestinians recognise Israel as a Jewish state -- and came out strongly against Prime Minister Benjamin Netanyahu's emphasis on it, just days before Abbas's visit.
"'Jewish state' was resolved in 1947 in (UN) Resolution 181 where there are more than 30 to 40 mentions of 'Jewish state,'" Kerry testified at a Congressional hearing Thursday, adding late Palestinian leader Yasser Arafat had already accepted the idea of a Jewish state in principle.
"I think it's a mistake for some people to be raising it again and again as the critical decider of their attitude toward the possibility of a state and peace, and we've obviously made that clear," Kerry said, referring to repeated statements by Netanyahu, who himself visited the White House on 3 March.
Current Palestinian leaders have opposed recognising Israel as a Jewish state, fearing this could threaten the rights of non-Jewish Arabs living in Israel, who make up some 20 percent of the population, as well as other religious minorities.
And even without the "Jewish state" stumbling block, it is unclear whether the Palestinians would accept an extension of negotiations, with Abbas saying cautiously that they will only decide if the US framework is acceptable once they have seen it.
"Until now, we haven't received the framework agreement we were promised," Abbas said at a Thursday news conference alongside visiting British Prime Minister David Cameron.
"When the framework is presented to us, we'll give our opinion on it," Abbas said.
"We have never discussed prolonging the negotiations at all, nor was it offered to us," he added.
Both Kerry and Cameron cited what they said was deep "mistrust" between Israeli and Palestinian leaders, but expressed hope Abbas and Netanyahu would soldier on towards an elusive peace deal.
"As for the question of mistrust between Palestinian leadership and Israeli leadership... what I've seen over the last few days is serious disagreements on vital issues that will have to be settled if there ever is to be... a peace deal," Cameron said.
Meanwhile, Kerry said there were "gaps... some of them very significant", but stressed these should be seen within the context of the negotiations, saying: "I still believe it's possible, but difficult."
"Certain narrative issues are so powerful and so difficult that neither leader is going to definitively cede on them at an early stage of the negotiation," Kerry conceded.
The issues include the contours of a future Palestinian state, refugees, the fate of Jerusalem, security and mutual recognition.
The Palestinians want borders based on the 1967 lines from before the Six-Day War, when Israel captured the West Bank, including now-annexed Arab east Jerusalem. They have also insisted there should be no Israeli troops in their future state.
But Israel wants to retain existing settlements it has built inside occupied Palestinian territory over the past decades. It also wants to maintain a military presence in the Jordan Valley, where the West Bank borders Jordan.
The Palestinians are also awaiting the release late March of a final of four batches of long-serving prisoners by Israel -- a commitment that Israeli ministers have hinted might be shirked.