Mark Laity reports on the sombre atmosphere at Rambouillet as talks enter a second week

Speaking in his weekly radio address, Mr Clinton said there were "serious obstacles" to overcome, but it was increasingly clear that the current peace plan could only succeed if it included "a Nato-led peace implementation force giving both sides the confidence to lay down their arms".

The need for a deal was underlined by reports from Kosovo which said at least nine people were injured in a bomb explosion in the central town of Urosevac.

International peace verifiers investigating the blast said there was no word on who was responsible.

Correspondents say bombings have become increasingly frequent in the province with Serb or ethnic Albanian cafes often being the target.

Meanwhile, outside the talks venue - a chateau just outside Paris - riot police were deployed to keep back thousands of pro-Albanian sympathisers.

Many of them carried the red Albanian flag and banners in support of the rebel Kosovo Liberation Army. There were no reports of any violence.

Strong peace

In his address, Mr Clinton said the deployment of American troops would depend upon the parties reaching a strong peace agreement. He said the Nato mission should be well defined.

"The time to stop the war is right now. Violence we fail to oppose leads to even greater violence we will have to oppose later at greater cost," he said.

The US toops would be led by British forces already on their way to the region

Moscow has warned the West not to make the force an explicitly Nato operation. The US troops are expected to form part of a British commanded mainly European force around 30,000-strong.

The Russian delegation is due to join western foreign ministers in Paris on Sunday to decide how to give more impetus to the talks. Saturday was the deadline set by Nato for the negotiators to make progress, but there has been little agreement so far after a week of negotiations.

There was meant to have been substantial progress by both sides before they would be allowed another week of negotiations.

Stonewalling tactics

Sources are saying that the Serbs in particular are continuing their stonewalling tactics. The Albanian delegation insists on the Serbs agreeing to an interim settlement with a guaranteed referendum on independence, something the Serbs will find hard to swallow.

Bridget Kendall reports: Some officials say the talks' chances of success are less than 50-50

Nonetheless it is expected that the six-nation Contact Group will give the go-ahead for a further week of talks.

On Friday, Nato Secretary-General Javier Solana warned that the West was losing patience with Belgrade over its refusal to engage in proper negotiations.

US Secretary of State Madeleine Albright is expected to throw her political weight behind the talks with a visit to the chateau at Rambouillet on Sunday. Officials said Ms Albright was going to "conduct her own on-the-ground assessment".

Albanian delegates seek a referendum on independence for Kosovo

The 15 foreign ministers of the European Union will also gather in Paris to add further pressure on the two sides.

Differences within the Contact Group also have yet to be resolved with the Russians continuing to object to the proposals on security which will see Kosovo virtually demilitarised and a Nato-led force implementing any deal.

The BBC's Defence Correspondent say that as a result it is thought there have been minor amendments which may include seeking UN Security Council authorisation for the force, something Washington believes is not needed.

Nato threats

Nato has threatened air strikes against Yugoslav targets if Belgrade jeopardises the negotiations aimed at bringing the conflict in the province to an end.

Mr Milutinovic, a close ally of Yugoslav President Slobodan Milosevic, warned that any Nato attack would prove disastrous.