U.S. Secretary of State John Kerry headed back to the Middle East on Monday for talks with Israeli and Palestinian leaders as peace talks have reached a critical make-or-break point.

The State Department said Kerry was flying from Paris to Tel Aviv for meetings that may be held in Jerusalem and Ramallah. Kerry spoke Monday with leaders from both sides as well as with the White House before deciding to go.

American mediators have been holding urgent talks with the two sides in hopes of salvaging the troubled negotiations and getting them to extend the talks beyond a current late-April deadline. With the parties unable to agree on the terms of a promised Israeli prisoner release, the negotiations risk collapse in the coming weeks.

Under heavy pressure from Kerry, Israel and the Palestinians agreed last July to hold nine months of peace talks, setting a late-April deadline for a final agreement. When that became unrealistic, Kerry scaled back his goals and said he would aim for a preliminary “framework” agreement by April, with the goal of continuing negotiations through the end of the year to iron out the final details of a deal.

But even that more modest goal has run into trouble due to a snag over the prisoner release. When the talks began last summer, Israel promised to free 104 long-serving Palestinian prisoners in four stages, with the final release coming by the end of March. After carrying out the first three releases, Israel has balked at releasing the final group without a Palestinian commitment to extend talks.

Israeli officials say they are under no obligation to carry out the final release because of what they say is a Palestinian failure to negotiate in good faith.

Yuval Steinitz, a Likud Cabinet minister, said “it is clear” the release can’t be carried out if Palestinian President Mahmoud Abbas plans on walking out of the talks the next day. “This release was meant to be carried out as the talks proceed, and not when they fall apart.”

Mohammed Ishtayeh, an aide to Abbas, accused Israel of “trying to blackmail us.” But Palestinian officials stopped short of threatening to walk out of the talks altogether. The chief Palestinian negotiator, Saeb Erekat, confirmed that negotiations were ongoing and said Abbas was “making every possible effort” to ensure the release of the fourth group.

Kerry met Sunday in Paris with Russia’s foreign minister about the Ukraine crisis. After his meetings in Israel and the Palestinian territories, he was planning on flying to Brussels on Tuesday for a meeting of NATO foreign ministers.

(AP)