British Foreign Secretary Margaret Beckett urged caution on Tuesday over the "swift resolution" on Iran dispute over 15 detained British Navy personnel.

"I would urge you to be cautious in thinking that we are likely to see a swift resolution to this issue," Beckett told reporters.

"Our diplomatic efforts will continue and continue intensively," said she.

Earlier Tuesday, British Prime Minister Tony Blair said the next two days would be "fairly critical" in the bid to secure the release of the 15 captured British sailors, and he warned Britain would "take an increasingly tougher position" if "peaceful, calm negotiation" to get the sailors back was not possible.

Beckett said that Blair was "not intending to imply anything about military action."

"We are not seeking confrontation. We are seeking to pursue this through diplomatic channels," she said.

On March 23, 15 British naval personnel were seized by Iranian forces when they were patrolling off the Iraqi borders.

Iran has insisted that the British boats illegally entered its territorial waters. But Britain said its soldiers were in Iraqi territorial waters.

Iran's tension with Britain has escalated dramatically since Tehran aired footage of the detained sailors for three times and a furious protest was staged Sunday outside British embassy in Tehran by Islamist students.

However, after a 12-day standoff, some conciliatory tones have surfaced from both sides in the past 24 hours, raising hopes of resolving the crisis soon.

Iran's chief nuclear negotiator Ali Larijani said on Monday Iran's priority is to resolve the problem through proper diplomatic channels, and "there's no need to have a trial on the detained sailors".

The British government responded later Monday by saying "we confirm we share his (Larijani) preference for early bilateral discussions to find a diplomatic solution to this problem."