* Palestinian leader furious over delayed prisoner release
* Kerry drops trip to region meant to sew up talks deal
* Deal, including partial settlement freeze, now seen at risk (Updates with Kerry cancelling talks with Abbas, Previous JERUSALEM)
By Ali Sawafta and Noah Browning
RAMALLAH, West Bank, April 1 (Reuters) - Palestinian President Mahmoud Abbas signed more than a dozen international conventions on Tuesday, citing anger at Israel's delay of a prisoner release in a decision that jeopardised U.S. efforts to salvage fragile peace talks.
His unexpected move was aimed at solidifying the standing of Palestinians in global bodies, defying both Israel and the United States that have long opposed such unilateral action.
U.S. Secretary of State John Kerry immediately announced that he was cancelling a trip to the region on Wednesday that Washington had hoped would result in a three-way deal aimed at extending the negotiations into 2015.
"This is a moment to be really clear-eyed and sober about this process," Kerry told reporters in Brussels, where he was attending a ministerial meeting of NATO.
"It is completely premature tonight to draw any kind of judgment, certainly any final judgment, about today's events and where things are," he said, making clear that he would pursue his efforts to end the generations-old Middle East conflict.
"We are continuing even now as I am speaking, to be engaged with both parties to find the best way forward."
Abbas had pledged not to seek to join world bodies during the U.S.-brokered negotiations, which are scheduled to run until the end of April and have made little apparent headway so far.
Israel had promised in exchange to free more than 100 prisoners by the end of March, but failed to release the final batch, saying it wanted guarantees that the Palestinians would extend the negotiations beyond the April 29 deadline.
Kerry made an unscheduled visit to Jerusalem on Monday seeking to overcome the impasse by putting together a complex package that included the possible release of Jonathan Pollard, an Israeli spy jailed in the United States in the 1980s, and hundreds of Palestinians held by Israel, as well as a possible partial freeze on Israeli settlement in occupied territory.
He had hoped to wrap up the accord on Wednesday.
Pollard, a U.S. citizen and former navy analyst, is serving a life term after being convicted of spying for Israel. His early release would be a political triumph for Netanyahu, making it easier for the Israeli leader to sell further Palestinian prisoner releases to a sceptical Israeli public.
In his remarks to Palestinian leaders in the West Bank city of Ramallah, Abbas made clear he did not want to abandon the negotiations, but blasted Israel's delay in freeing prisoners.
"We are not doing this against America, but we still don't see other ways forward," Abbas said, before signing a packet of papers Palestinian officials said included 15 conventions of international and U.N. groups.
Precise details of what he had signed were not given, but a senior Palestinian official, Mohammed Shtayyeh, told Reuters that one of the documents was the Geneva Convention, which lays down the standards of international law for war and occupation.
Signing the convention would give Palestinians a stronger basis to accede to the International Criminal Court and eventually lodge formal complaints against Israel for its continued occupation of lands seized in the 1967 war.
Israel and the United States are opposed to any move by the Palestinians to join world bodies, saying the only way they can gain a sovereign state is through direct negotiations. The U.S. Congress has acted in the past to halt financial aid to the Palestinians when they have joined international agencies.
Shtayyeh said the Palestinians had had no choice after Israel had failed to push ahead with the prisoner release.
"What has been done by the Palestinian leadership tonight is actually something the Israelis instigated by breaking the deal," he told Reuters.
There was no immediate response from Israel.
Palestinians also responded angrily to Israel's publication of tenders on Tuesday for construction of more than 700 homes in occupied East Jerusalem. Israeli officials said the publication was a repeat of an earlier bid that had failed to draw buyers.
Israeli settlements on West Bank and East Jerusalem land which Palestinians seek, along with the Gaza Strip, for their state have been a major stumbling block in the talks that began in July. Most countries view those settlements as illegal.
A source close to the talks held on Monday and Tuesday between Prime Minister Benjamin Netanyahu and Kerry said that Israel was prepared to consider a partial freeze on settlement building as part of a broad arrangement to extend peacemaking. (Additional reporting by Lesley Wroughton in Brussels and Allyn Fisher Ilan in Jerusalem; Editing by Crispian Balmer/Mark Heinrich)