Nato troops are likely to remain in Bosnia and Kosovo as long as President Slobodan Milosevic holds on to power in Yugoslavia, the alliance's military chief has said.

Nato's supreme commander in Europe, General Wesley Clark, told the US Congress that for the conflicts in the Balkans to be peacefully resolved, Mr Milosevic would have to go on trial for war crimes, and democracy would have to be introduced to Yugoslavia.

His comments came only hours after Mr Milosevic demanded that Nato-led peacekeepers (K-For) and United Nations administrators withdraw from Kosovo.

General Clark told the House Armed Services Committee there was "still a threat" the Yugoslav president would trigger another war.

Mr Milosevic was forced to withdraw his troops from Kosovo last June after Nato's 11-week air campaign against Belgrade's military crackdown on the separatist ethnic Albanian majority in the province.

Eight months on from the air strikes, the general said Mr Milosevic's military was once again in training, with "some generals talking about going back into Kosovo". General Clark said Mr Milosevic might also have his eye on pro-Western Montenegro.

'Peaceful resolution'

US lawmakers have become increasingly frustrated over the extent and length of America's commitment to the peacekeeping effort in Kosovo and Bosnia. About 6,000 of the 50,000 troops in Kosovo are American.

However the general refused to put a timeframe on any withdrawals.

"The key to a peaceful resolution and a successful exit from the region for US forces and the forces of Nato is democratisation in Yugoslavia and Mr Milosevic's appearance at the international criminal tribunal in The Hague."

General Clark called for more international civilian police in Kosovo to ease the burden on military forces.

He added that it was crucial that economic measures against Yugoslavia were targeted only against Mr Milosevic and not the Serb population.

"Nato has never been anti-Serb. We've been anti-Milosevic," he said.

'Fiasco'

In Belgrade, the Yugoslav president was in defiant mood as he addressed his first party congress since the Nato air strikes.

Mr Milosevic told delegates of the Serbian Socialist Party (SPS) that the K-For and UN operations in the province had been a "total fiasco".

UN control should be ended as soon as possible and "the authorities of our country should take over their full control of this sovereign part of our territory", he said.

The demand followed a flare-up of armed violence in the divided town of Mitrovica, one of the last outposts of Serbs in the province and a flashpoint for ethnic tensions.

BBC Belgrade correspondent Jacky Rowland says the scenes outside the congress were reminiscent of communist times.

Peasants and workers were transported into the capital in order to praise Mr Milosevic's programme of reconstruction following Nato's raids.

Inside the conference hall, Mr Milosevic's speech was received with an ovation.

The Yugoslav president was also re-elected as party leader - he was the only candidate.