London ? Britain called for direct talks with Iran to resolve a dispute over 15 captive Britons on Tuesday after its first contact with the chief Iranian negotiator. The announcement followed the sudden release of an Iranian diplomat in Iraq that raised new hope for resolving the standoff.

In a statement late Tuesday, Prime Minister Tony Blair’s office said there had been “further contacts” between the two countries, including with chief international negotiator Ali Larijani.

“The UK has proposed direct bilateral discussions and awaits an Iranian response on when these can begin,” Blair’s office said. “Both sides share a desire for an early resolution to this issue through direct talks.”

Blair said earlier in the day that the next 48 hours would be “fairly critical” to resolving the standoff over the British personnel, who have been held by Iran since March 23.

The call for talks came hours after Iranian diplomat Jalal Sharafi was freed by his captors in Iraq. He had been seized Feb. 4 by uniformed gunmen in Karradah, a Shiite-controlled district of Baghdad.

His release raised hope for an end to the standoff and suggested the possibility of a de facto prisoner swap – something both Tehran and London have publicly discounted.

Iran alleged the diplomat had been abducted by an Iraqi military unit commanded by U.S. forces – a charge repeated by several Iraqi Shiite lawmakers.

U.S. authorities denied any role in his disappearance.