In a statement from 10 Downing Street he made it clear that Britain feels Iraq's offer to let UN weapons inspections resume is enough to ward off immediate air strikes.

He said military forces would remain on alert and attack without warning if Iraqi President Saddam Hussein broke his promises.

BBC Correspondent Cary Johnston: Strikes still an option - tension in the region is still running high

"We need to be sure that every bit of this is bolted down. Saddam Hussein needs to know that we remain ready, willing and able to strike," Mr Blair said.

"This is not over until absolute and unconditional compliance is guaranteed and delivered."

Earlier UK Foreign Secretary Robin Cook told the BBC that Iraqi diplomats had clarified overnight that their offer was unconditional.

And he warned if the agreement was broken there would be international support for "swift and heavy" action from the forces stationed in the Gulf.

LSE Professor Fred Halliday says it is possible Saddam Hussein miscalculated

US Secretary of State Madeleine Albright announced she was cutting short her trip to the Asia Pacific summit in Malaysia

"We are very carefully assessing more recent statements of some significance," she announced before her return to Washington. "All options remain on the table".

After a night of intense diplomatic activity the United Nations Security Council adjourned until later on Sunday after failing to decide on its response to the Iraqi offer.

The letter clarifying Iraq's offer was unconditional

France, Russia and China welcomed the Iraqi move.

Earlier, Pentagon officials confirmed that a massive cruise missile attack was aborted on Saturday after Iraqi Deputy Prime Minister Tariq Aziz wrote to the UN detailing Baghdad's new policy.

Reports suggest President Clinton called off the attack less than an hour before it was scheduled to begin.

Iraqi ambassador Nizar Hamdoon: The offer is unconditional

Iraq's Ambassador to the UN, Nizar Hamdoon, delivered a second letter to the council confirming that Iraq's offer to allow the resumption of inspections was "clear and unconditional".

US and UK doubts over the Iraqi offer were concerned with a two-page annex in Iraq's original letter which reiterated Baghdad's previous terms for a comprehensive review of the inspection process and sanctions.

US National Security Adviser Sandy Berger said the annex meant the offer was equivocal and conditional. He said it had "more holes than Swiss cheese".

Mr Blair and President Clinton consulted nine times during the night before apparently deciding that Baghdad's latest offer to allow UN weapons inspections to resume, was enough to avert immediate air strikes on Iraq.

The US president cancelled a foreign visit to concentrate on developments concerning Iraq.

Vice-President Al Gore would represent Mr Clinton at the Asia Pacific Forum meeting taking place in Malaysia.