UK Prime Minister Tony Blair spoke by telephone to the Finnish President Martti Ahtisaari after the EU's Balkans peace envoy had spoken to President Milosevic.

UK Government officials say "the indications from Mr Ahtisaari's call to Milosevic were that Milosevic was getting back in line".

Mr Blair also spoke to US President Bill Clinton and German Chancellor Gerhard Schröder.

The prime minister's spokesman said "work on all the options continues to be carried out" as the search for a resolution to the crisis continued.

The comments from Downing Street came as European and Russian foreign ministers agreed on a new resolution on the withdrawal of Serb forces at a meeting in Germany.

And a session of the United Nations Security Council has been called in anticipation of a draft resolution being agreed to end the war in Kosovo.

Foreign ministers from the G8 group of nations, which includes Russia, are said to be narrowing their differences on the draft text, but agreement is not expected until Tuesday.

'Bad faith and trickery'

Earlier, the UK Defence Secretary George Robertson blamed the Serbs for the collapse on Sunday of the talks aimed at securing the withdrawal of their forces from Kosovo.

Mr Robertson said that as a result of Serbian "bad faith and procedural trickery" Nato was left with no alternative but to step up its air campaign over Yugoslavia.

He said: "The only reason the talks broke down was the refusal of Belgrade to keep to their word. It is as simple as that."

Speaking at a Ministry of Defence briefing he said: "I have no pleasure in saying that I was absolutely right to be cautious and sceptical about the willingness of Milosevic to stick to his word.

George Robertson: "This display of uncooperation is too familiar"

"Although Milosevic has been defeated he is going to use every trick in the book to escape the consequences."

Mr Robertson said stepping up the air campaign was the only way to ensure the safe return of the refugees to their homes.

He also said that all military options remain on the table.

Buring the evidence

The defence secretary added that the current delays by the Serbs to implement the agreement could perhaps be explained by a drive to destroy the evidence of any ethnic cleansing.

Robin Cook: Will meet G8 ministers

Mr Robertson added that reports of Serbs burning bodies sounded "all too credible".

Earlier Foreign Secretary Robin Cook described the collapse of the talks aimed at securing a Serbian withdrawal from Kosovo as a serious setback.

Mr Cook said the Kosovo peace talks stalled because Yugoslav military commanders insisted on maintaining a contingent of up to 15,000 Serb troops in the province.

He told the BBC it was impossible for Nato to halt its military campaign while the Serbs were continuing their offensive in Kosovo.

Robin Cook: "We need to wait and see what progress is made today before making a decision"

Nato spokesman Jamie Shea said President Milosevic had to stick with the commitments he had already made.

"They include of course accepting a force on his territory which will include a substantial number of Nato's forces," he said.

Shadow Foreign Secretary Michael Howard said he was prepared to support an intensified bombing campaign.

"It is certainly deeply disappointing the agreement was reneged upon.