In a surprise move that could derail U.S. peace efforts, Palestinian President Mahmoud Abbas on Tuesday resumed a campaign for further U.N. recognition of a Palestinian state, despite a previous promise to suspend such efforts during nine months of negotiations with Israel.

Shortly after Abbas’ announcement, U.S. Secretary of State John Kerry canceled plans to return to the Middle East today, but also said it’s “completely premature” to write off the Israeli-Palestinian peace talks he restarted in late July.

“We are continuing, even now … to be engaged with both parties,” Kerry told a news conference in Brussels, where he was attending a meeting of NATO foreign ministers. “We urge both sides to show restraint while we work with them.”

There was no immediate Israeli comment. However, Abbas’ decision threw into doubt Israeli claims that a deal was emerging that would have extended Israel-Palestinian talks beyond an April 29 deadline and included the release of imprisoned spy Jonathan Pollard.

It remained unclear whether Abbas’ dramatic announcement was a negotiating tactic or signaled a fundamental shift in strategy.

In a hastily convened ceremony televised live from his West Bank headquarters, Abbas signed “State of Palestine” applications for 15 U.N. agencies and conventions, and said the Palestinians would launch the applications process immediately.

Abbas said he was compelled to act because Israel had failed to carry out a promised release of Palestinian prisoners by the end of March.

At the same time, Abbas said he is not seeking a confrontation with the United States and remains determined to “reach a peaceful solution through negotiations” with Israel.

A senior aide, Nabil Abu Rdeneh, later urged the international community to pressure Israel to release the prisoners, indicating that the Palestinians might reverse course if their demand is met.

Still, Abbas’ surprise decision signaled a new crisis in Kerry’s troubled peace efforts.

Kerry had nudged Israelis and Palestinians back to the table in July, after a five-year break in negotiations, and got them to commit to nine months of negotiations, until April 29. The target was to reach a framework deal on the terms of a Palestinian state alongside Israel.

As part of that deal, Abbas promised to suspend Palestinian efforts to seek further U.N. recognition for the duration of the talks, including applying for Palestinian membership in U.N. agencies, treaties and conventions.

The U.N. General Assembly recognized a Palestinian state in the West Bank, Gaza and east Jerusalem — lands Israel occupied in 1967 — as a non-member observer in a vote in November 2012, overriding Israeli and U.S. objections.

In exchange for Abbas’ promise, Israel pledged to release 104 of the longest-held Palestinian prisoners who had been locked up since the early 1990s. The Palestinians say the fourth and final group was to have been released by the end of March. Israel argues that the release was contingent on the Palestinians negotiating “in good faith.”

In recent days, Kerry has been trying to negotiate a deal on extending the talks until the end of the year. An Israeli official close to the negotiations said earlier Tuesday that Kerry was pushing a formula that would include Pollard’s release.

In exchange for Pollard, Israel would free the last group of 26 Palestinian prisoners, show “restraint” in settlement building and release about 400 additional Palestinian prisoners it would select.