In a powerful speech in Washington, Mr Clinton insisted that the bombing would continue as long as it took to convince the Yugoslav leader to agree to Nato's demands.

"The Kosovars must be able to return home and live in safety," he said.

President Clinton: Kosovo is a moral and strategic issue

The BBC Washington Correspondent Paul Reynolds said President Clinton was seeking to reassure those concerned by the failure of the air campaign to break Serb determination and by the crisis with Russia and China.

In his speech, Mr Clinton went on to justify the Nato campaign, giving details of the atrocities carried out by Serb forces against Kosovo Albanians.

Holocaust comparisons

He compared President Milosevic's ethnic cleansing with the Holocaust.

He said that although the two were not the same, they were related - "both vicious, premeditated, systematic oppression, fuelled by religious and ethnic hatred".

Mr Clinton said that if the US and its allies were to ignore ethnic cleansing, "all we would do is create an environment for that sort of practice, and a world of trouble for Europe and the US in years ahead".

Serbian human rights abuses have also been attacked by the United Nations High Commissioner for Human Rights, Mary Robinson.

John Simpson reports on Mary Robinson's visit amidst continued bombing

During a visit to Belgrade, she said Yugoslavia had to commit itself to the unconditional and safe return of all refugees.

She said she regretted that President Milosevic had refused to meet her because she wanted to bring directly to his attention the need to punish those responsible for the abuses.

But she tempered her criticism by saying the Nato strikes had brought cruel suffering to innocent civilians in Yugoslavia.

Raids stepped up

Nato was given a boost by news from Germany, where the Green Party voted against a pacifist motion and instead supported the country's continued involvement in the Nato attacks on Yugoslavia.

Bridget Kendall reports on growing opposition to Nato action

Nato has also been strengthened by the US's announcement of the deployment of an additional 35 aircraft.

The alliance has kept up the pressure on Serb forces in Kosovo by mounting raids during daylight hours.

(Click here to see a map of last night's Nato strikes)

In its latest damage assessment, it said that on Wednesday it had destroyed a further five Serb aircraft on the ground, bringing the total to 100.

Overall, Nato said it had destroyed 40% of artillery, 25% of armour and most of the ammunition and fuel for the forces operating in Kosovo.

It also said it had indications that the number of Serb troops killed was considerably higher than first estimated.

Nato denied evidence of a Serb withdrawal from Kosovo

Yugoslavia appears to have acknowledged its military losses, with President Milosevic paying tribute to Serbian soldiers who he said had been killed in the Kosovo conflict.

However the alliance has said that a Serb defeat could still be some way off.

The US forces senior military commander, General Hugh Shelton, said there were significant signs of growing unrest and discontent among the Serb forces, but acknowledged they could hold out for some time to come.

The alliance also played down reports that 250 Serb troops had pulled out of Kosovo.

Nato's military spokesman, General Walter Jertz, said the alliance had no proof of any withdrawal and that any troop redeployment was a tactic forced by the air strikes.

French intervention

As Nato pressed on with its strikes, diplomatic efforts continued to try to find a way out of the crisis.

French President Jacques Chirac said his talks with Russian leaders in Moscow had brought some progress. He said he was sure Russia would not end its bid to mediate in the crisis despite threats to do so.

Russian President Boris Yeltsin was earlier reported to have warned his French counterpart that Moscow might reconsider its role in peace efforts if Nato continued to bomb Yugoslavia.

Mr Clinton also sought to soften the harshness of recent relations with Russia and China.

In his speech, he repeated a welcome for Russian troops in an international force for Kosovo and expressed his personal sadness at the casualties of the Chinese embassy in Belgrade.

• Refugees recount fresh atrocities
• Greens back leader over Nato
• Analysis: Sacking could boost Kosovo peace
• Bulgaria says Nato bombing will succeed
• Macedonia complains over Nato aid

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