TEHRAN, Iran — President Mahmoud Ahmadinejad defused a growing confrontation with Britain, announcing the surprise release of 15 captive British sailors Wednesday and then gleefully accepting the crew’s thanks and handshakes in what he called an Easter gift.

Hours later, the 15 Britons arrived at the VIP section of Tehran’s airport in a convoy of sedans and were expected to board a British Airways flight to London at 8 a.m. local time Thursday today.

The convoy was escorted by several cars belonging to Iran’s Revolutionary Guards, the elite force whose naval units seized the sailors on March 23 as they searched the Persian Gulf for smugglers.

British Prime Minister Tony Blair expressed “profound relief” over the peaceful end to the 13-day crisis. “Throughout we have taken a measured approach — firm but calm, not negotiating, but not confronting either,” Blair said in London, adding a message to the Iranian people that “we bear you no ill will.”

The announcement in Tehran was a breakthrough in a crisis that had escalated over nearly two weeks, raising oil prices and fears of military conflict in the volatile region. The move to release the sailors suggested that Iran’s hard-line leadership decided it had shown its strength but did not want to push the standoff too far.

Iran did not get the main thing it sought — a public apology for entering Iranian waters. Britain, which said its crew was in Iraqi waters when seized, insists it never offered a quid pro quo, either, instead relying on quiet diplomacy.

Syria, Iran’s close ally, said it played a role in winning the release. “Syria exercised a sort of quiet diplomacy to solve this problem and encourage dialogue between the two parties,” Syrian Foreign Minister Walid al-Moallem said in Damascus.

The announcement of the release came hours after U.S. House Speaker Nancy Pelosi met with President Bashar Assad in Damascus, trying to show that a U.S. dialogue with Syria — rejected by the Bush administration — could bring benefits for the Middle East. The British sailors were not part of their talks, and it was not clear if the release was timed to coincide with her visit.

Several British newspapers credited Blair’s foreign policy adviser Nigel Sheinwald and Iranian chief negotiator Ali Larijani with laying the groundwork for an agreement during telephone contacts that began Tuesday night. Larijani had gone on British TV on Monday and signaled that Tehran was looking for a diplomatic solution.

British officials were told to pay close attention to Ahmadinejad’s press conference but were unsure the release would come until they heard his words, The Independent newspaper said.

Ahmadinejad timed the announcement so as to make a dramatic splash, springing it halfway through a two-hour news conference.

“This pardon is a gift to the British people,” he said.