Israeli and Palestinian negotiators have met US envoy Martin Indyk to try to find a way to extend faltering peace talks, with one Palestinian source calling the discussion "difficult".
The meeting, which had been put off by a day, began in the late afternoon in a Jerusalem hotel, Palestinian sources said on Thursday.
The discussions are "very difficult", one source said.
Israel implied that the delay had been caused by the killing of an Israeli police officer in the West Bank this week, but the Palestinians said the meeting was pushed from Wednesday to Thursday to enable Indyk to take part.
Israeli and Palestinian negotiators met on their own on Sunday and held a three-way meeting with Indyk a week ago in last-ditch efforts to save the stagnant peace process launched by US Secretary of State John Kerry in July for a period of nine months.
State Department spokeswoman Jennifer Psaki said this week that Israeli and Palestinian negotiators are striving to reach an agreement to extend the talks beyond their April 29 deadline.
Washington is pushing for an extension but the negotiations hit an impasse two weeks ago when Israel refused to release a group of Palestinian prisoners as agreed at last year's launch of the talks.
Under the agreement, Israel had committed to free 104 prisoners held since before the 1993 Oslo autonomy accords in four batches, but it cancelled the release of the last group of 26.
Among them are 14 Arab Israelis who the Jewish state is refusing to set free.
The Palestinians retaliated by seeking accession to several international treaties.
Despite the crisis, Palestinian president Mahmud Abbas's spokesman Nabil Abu Rudeina stressed the talks could be extended if Israel released the last batch of prisoners.
"What's needed now is Israel's commitment on issues that could lead to an extension of talks. If they commit, we're ready," he said on Wednesday.
