Israeli and Palestinian negotiators met Thursday with 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.

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 2013 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 peace accords in four batches, but it canceled the release of the last group of 26. Among them are 14 Arab Israelis.

The Palestinians retaliated by seeking accession to several international treaties.

Prisoners Day rallies

Thursday’s new round of talks came as Palestinians marked Prisoners Day with rallies across the West Bank and Gaza Strip in solidarity with thousands of their jailed compatriots.

Chief Palestinian negotiator Saeb Erekat added his voice to the protesters on Thursday by calling anew on Israel to free the last batch of prisoners.

And prisoners minister Issa Qaraqe said on Voice of Palestine Radio that signing up to international treaties, including the Fourth Geneva Convention, could pave the way to prisoners’ rights.

Despite the crisis, Palestinian Authority President Mahmoud Abbas’s spokesman Nabil Abu Rudeineh 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.

And Abbas told Israeli opposition MPs visiting him in the West Bank administrative center of Ramallah he would insist that the 14 Arab Israelis were among those released, Haaretz newspaper reported.

It said that if talks were extended, Abbas would want the first three months to be “devoted to a serious discussion of borders.”

The Palestinians want a state based on the lines that existed before Israel captured the West Bank and Gaza in the 1967 Six-Day War.

According to Channel 2 television, Israel’s Shin Bet domestic security agency head called for 10 of the 26 prisoners slated for release to be deported abroad or transferred to the Gaza Strip.

Progress in the peace talks has stumbled over all key issues, namely borders, Jewish settlements, security, the status of Jerusalem and the fate of Palestinian refugees.