COLOMBO (Reuters) -- Suspected Tamil Tiger suicide bombers sank a small naval boat off Sri Lanka's east coast early on Saturday and 13 of the 15 crew were missing, the navy said, in the latest of a series attacks on the military.

Nearby fishermen pulled two sailors alive from the water after the pre-dawn attack on the fast attack craft just outside Trincomalee naval harbor, and the Navy was searching for the rest of the crew, all initially feared to have died.

One of the survivors said a Tiger vessel had rammed their boat and exploded, destroying both vessels, a military source said.

Suspected rebels have threatened to resume an armed struggle unless given wide autonomy. In December, 39 military personnel were killed in a string of mine attacks, the deadliest month since a 2002 cease-fire that diplomats and truce monitors say is strained to breaking point.

Officials said crews searching the Trincomalee site after daylight could not even find debris from the two vessels. "We believe it was a Tiger suicide mission. The dora was completely destroyed," said Navy spokesman Commodore Jayantha Perera. "We're still looking for the 13 missing."

The Liberation Tigers of Tamil Eelam (LTTE) were not immediately available for comment, but have routinely denied any hand in attacks on the military -- which analysts and the government say they cannot believe.

Suspected rebel attacks escalated after the Tigers helped sink the chances of the candidate seen as most likely to reach a peace deal by boycotting November's presidential poll, which analysts say shows they are using the truce to regroup and rearm. The Tigers say they want a political solution to the conflict, which has killed more than 64,000 people and displaced hundreds of thousands more since 1983. But they also say they are ready for war unless they are given an ethnic homeland in the north and east, where they already run a de facto state. -- ------------Search for peace

New President Mahinda Rajapakse's government and the rebels cannot even agree on a venue for crunch talks, with the Tigers demanding they should be held in Europe and the government insisting on Asia or at home.

Norwegian peace envoy Erik Solheim is due in Sri Lanka on Jan. 23 to try to break the deadlock, and the government has put the onus on him to sort out the venue. Analysts say both sides will have to compromise or risk facing a very grim scenario.

Foreign Minister Mangala Samaraweera, capping an official visit to Washington where he sought American help to avoid a slide back into war in the island state, said Colombo was "still willing to walk that extra mile for peace".

"This is not because of any weakness but because we are a government committed to a negotiated settlement to this problem and we do not think that war is an option," he told reporters.

"We want to bring international pressure on the LTTE to come and sit with us at the table to discuss the weaknesses of the cease-fire and find ways and means of strengthening it so these dastardly acts do not happen again," Samaraweera added.

The United States banned the LTTE in 1997 and U.S. forces have been training Sri Lankan troops, but diplomats in Colombo say there is no chance Washington would wade in militarily if the violence spirals into war.

Samaraweera called the Tigers a "brutal terror machine" and said the government feared a possible backlash if the violence continued.

"We are a government committed to a negotiated settlement to this problem and we do not think that war is an option," he told reporters in Washington. "There will come a point where the public would be provoked into actions which the government may not be able to control."