Prime Minister Tony Blair's office sought to calm fears Monday that a dispute over the capture of a British navy crew would deepen tensions between Teheran and the West, as Iran said it was interrogating the 15 British service personnel accused of illegally entering Iranian waters. The detention of the Britons appeared likely to worsen relations with Iran at a time when Teheran is at odds with the West over its nuclear program and is accused of interfering with the Iraq war. But Blair's spokesman said the prime minister intended to treat the seizure of naval personnel as a distinct issue. "This is a matter that should be dealt with on its own merits," he said. Blair said Sunday he hoped the situation could be resolved in as diplomatic a way as possible, and his office stressed the British leader had been "very careful when he intervened," mindful of the potential repercussions on other issues.