Bitter divisions between Israel and the Palestinians were Saturday complicating intense efforts by US Secretary of State John Kerry to craft a framework for the next crunch months of peace negotiations.
After mostly sticking to pledges made in July not to air their grievances in public, the mutual distrust between the two sides has burst into the open with each accusing the other of trying to scupper the talks.
US officials have acknowledged that a sought-after agreement on a framework to guide the negotiations forward would not be reached on this trip, signalling Kerry may return to Israel soon.
The top US diplomat, who has made it a personal quest to reach a long-elusive peace deal, is on his 10th trip to the region since becoming secretary of state in March.
Only hours after meeting Palestinian president Mahmud Abbas for six hours over dinner Friday, Kerry's motorcade swept back into the Palestinian leader's West Bank headquarters in Ramallah on Saturday for another scheduled three hours of talks.
A new protest flared Saturday with about 200 Palestinian youths protesting against Kerry's trip outside the offices of the Palestine Liberation Organisation in the city.
On Friday, about 100 Palestinians from the left-wing Democratic Front for the Liberation of Palestine (DFLP) had protested in Ramallah's central square waving Palestinian and red flags.
Azzam al-Ahmed, a senior official of Abbas's ruling Fatah party, told Voice of Palestine radio that Kerry was proposing "various" ideas, but "these are closer to the Israeli position" than the Palestinian one.
"If he continues to stick to these ideas, then we are not optimistic of reaching a framework agreement or a comprehensive peace deal by the end of April," said Ahmed.
But Israeli daily Haaretz quoted Kerry as telling American students on Friday that he remained hopeful.
"I am a believer in the possibility... we could achieve something," Haaretz quoted him as telling students in an impromptu appearance at a gathering at his Jerusalem hotel. "But it will be very, very difficult."
One student was quoted as saying that Kerry explained he was "wading through a volatile cocktail of issues".
Kerry was due to meet Israeli Prime Minister Benjamin Netanyahu later Saturday in Jerusalem for their third round of talks in as many days.
Direct Israeli-Palestinian negotiations had been frozen for almost three years, but after intense diplomacy by Kerry the two sides agreed to resume talks in July and vowed to remain at the table for the next nine months.
With the late April deadline looming, Kerry has pledged to work even more intensively with the two sides in the coming months.
But he came under fire from veteran US Senator John McCain, who also met with Abbas on Saturday during a visit to the region.
McCain said he shared Netanyahu's worries about the emerging framework, and whether a deal would jeopardise Israel's security.
"Netanyahu has serious, serious concerns about the plan as has been presented to him, whether it be on the ability of Israel to defend its borders or the reliability of a Palestinian state and their intentions," McCain said after meeting the premier on Friday.
US officials have refused to release any details about the framework, which they hope to conclude soon.
Kerry stressed the framework was building on ideas from both sides over five months of talks, and would set out the agreements and disagreements on the core issues.
These included the contours of a future Palestinian state, refugees, the fate of Jerusalem, security and mutual recognition, Kerry said.
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.