Nato continued its air strikes on Thursday night, warning that the bombings would go on until Serb forces pulled out of Kosovo as promised.

Preparations are also under way to implement other key parts of the peace agreement.

A further 4,000 UK troops, including mine clearance experts, are being put on standby to join the forces waiting in Macedonia to help the refugees return home.

But Foreign Secretary Robin Cook said President Milosevic would not be "let off the hook" for his ethnic cleansing, despite rising hopes of an end to the conflict.

Speaking at the European Union summit in Cologne, he said the possibility of an amnesty or immunity had not even been raised by either side in the peace negotiations.

Robin Cook: No amnesty for war crimes suspects

Nato would do all it could to see the Yugoslav leader face the indictment brought against him by the independent International Criminal Tribunal for the former Yugoslavia.

"What we are quite clear about is that as an indicted war criminal like other indicted war criminals he has to face justice. He has to stand trial," Mr Cook said.

"There can be no lasting peace and settlement in Kosovo without justice against those who carried out the atrocities in Kosovo."

'Ample evidence'

Prime Minister Tony Blair agreed there could be no question of Mr Milosevic being granted immunity, even if the peace deal was fully implemented.

Mr Blair hopes the refugees can start returning home within weeks

Speaking from Cologne, he said the international force to help the refugees return home would also gather evidence against the Serb leadership.

The lst Battalion of the Parachute Regiment had been ordered to Macedonia to take part in a Kosovo peacekeeping force, Mr Blair revealed at the end of the summit.

"When we begin that process of going back into Kosovo and we find what has happened and we have a clear picture of what has been done, how many people have disappeared, died, been subject to brutality and barbarity, then we shall have ample evidence of the policies of Milosevic and the evils of ethnic cleansing," he said.

While insisting that Nato had never made President Milosevic's removal from office one of its aims, Mr Blair, said it would clearly be in Serbia's interests if he did go.

Tony Blair: We don't want a situation where Mr Milosevic will ever be able to do this again

"Serbia and the Serbian people probably know now - and we must make them more aware over the coming weeks - that there is no real place for Serbia in the family of nations while that man remains head of their government," he said.

While other countries in the region would receive EU funding to rebuild after the conflict, Serbia would be denied such help while Mr Milosevic remained in power, he added.

Serb withdrawal discussed

Nato says Serb forces must start to retreat before its bombing stops

In addition to committing more troops to Kosovo, Nato has also begun discussions with Belgrade on the logistics of a Serb withdrawal.

Mr Cook said the air campaign would go on until Mr Milosevic kept his word and pulled his forces out of Kosovo.

"We are not going to settle for promises from President Milosevic we need to see action," he said.

Air Marshall Sir John Day: Nato is working to enter Kosovo as soon as agreements are in place

Suggestions Nato was scaling down its air campaign to a token level of "show bombing" were denied by the UK's Deputy Chief of Defence.