In a televised address from the Oval Office, he said Serbia would get no aid for reconstruction while it was "ruled by an indicted war criminal".

But he said the US would be happy to help when the Yugoslav Government represented "tolerance and freedom, not repression and terror".

Mr Clinton told the American people that the air campaign against Yugoslavia had "achieved a victory for a safer world, for our democratic values and for a stronger America".

His speech to the nation came as the deployment of the international peacekeeping force in Kosovo was put back until late on Friday or early on Saturday.

The first K-For units had been expected to cross into the province from Macedonia at about 4am local time on Friday, but some troop-contributing countries were reported to have requested more time to assemble their forces.

The peace process has been moving so quickly that barely half the planned 50,000 force is ready.

George Ekyn reports: "The first moves into Kosovo will be by British and French troops"

American Black Hawk and Chinook helicopters have been ferrying in hundreds of soldiers from neighbouring Albania as the build-up continues.

British and French units are expected to be the first to enter the province, with the aim of securing routes into Kosovo.

BBC correspondent Ben Brown on the border says some UK SAS soldiers may already be inside the province to liase with the withdrawing Serbs over mines.

Diplomatic moves

The BBC's Brian Hanrahan: Legal support for Nato position

The United Nations Security Council approved the deployment on Thursday, after Nato announced an end to its bombing campaign.

The Security Council vote came after Nato verified that Yugoslav troops were beginning to withdraw from Kosovo.

China abstained and the official press on Friday said Beijing had serious reservations about the peace plan.

But a commentary in the People's Daily said it was Chinese pressure which had forced Nato countries to accept an amendment stressing the principles of the UN charter.

(Click here to see a map showing timetable of Serb withdrawal)

Russian involvement in peacekeeping operations in Kosovo is still under discussion, but Mr Clinton urged Moscow to contribute.

President Clinton addresses America

He said he was pleased that the US partnership with Russia had been preserved, despite disagreement over Nato's use of force in the conflict.

US Deputy Secretary of State Strobe Talbott held a second round of talks in Moscow with Foreign Minister Igor Ivanov on Friday to resolve differences which remain over the operation.

Mr Talbott said the crisis had placed US-Russian relations under their greatest strain since the end of the Cold War, but they had passed the test.

President Boris Yeltsin said that ties with Nato are still frozen, in spite of the suspension of the bombing campaign.

"Relations between Russia and Nato still remain frozen. As for the future, we will see," Mr Yeltsin said in a statement on Friday.

Russia demands an independent command and a separate sector for its peacekeepers - both of which Nato rejects.

If Moscow did not get what it wanted, a senior general said on Friday, it would bypass Nato and declare its own sector in agreement with Yugoslavia.

In Belgrade, President Milosevic told the Serbs that the international troops in Kosovo would be under United Nations' command.

Broadcasting to the nation for the first time since the air strikes began, he praised the armed forces and his own policies which, he said, showed that Yugoslavia had the greatest army in the world.

Aid operations

Humanitarian operations will resume once Kosovo is under K-For control.

The UN refugee agency, the UNHCR, has said it will initially run convoys to the tens of thousands of people who have spent many weeks living rough in Kosovo.

The situation on the ground remains volatile. On Thursday, Serb units opened fire on Kosovo Liberation Army soldiers withdrawing from a village in southern Kosovo, a senior officer said.

Nato has warned that it will be watching closely to see that a ceasefire remains in effect.

It has also held extensive contacts with the KLA to try to ensure it does not attack retreating Serb forces.

KLA commanders have told a BBC team inside Kosovo that while the ethnic Albanian guerrillas will welcome Nato, there is no immediate intent to lay down their arms.

K-For commander General Mike Jackson said his troops would be robust in dealing with both sides.

"Violence or non-compliance, wherever it may come from, will not be tolerated," he said.

• Eyewitness: Inside Kosovo
• K-For: The task ahead
• Serb civilians may flee Kosovo
• Refugees warned over return
• Serbs reflect on 'victory'