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.
Iran's official news agency said the British crew was to leave Iran by plane on Thursday at 8 a.m.