The fraught Mideast peace talks were thrown into confusion on Tuesday as a meeting between Secretary of State John Kerry and President Mahmoud Abbas of the Palestinian Authority was canceled after Mr. Abbas moved to join 15 international agencies, a move vigorously opposed by Israel and the United States.

Mr. Abbas, who has been under pressure from other Palestinian leaders and the public to press his case for statehood through United Nations agencies, said Tuesday that he was taking that course because Israel had failed to release a fourth batch of long-serving Palestinian prisoners by the end of March, as promised when the talks started last summer…

Mr. Kerry, who had flown from Israel to Brussels for a NATO meeting on Tuesday and was planning to return to see Mr. Abbas in Ramallah, West Bank, on Wednesday, said he was no longer making the trip.

It was unclear from his remarks whether Mr. Kerry or Mr. Abbas — or both — had canceled the meeting. Nor was it clear what the cancellation might mean for the peace talks, but Mr. Kerry insisted at a news conference in Brussels that the peace process was not dead.