As efforts continue in Moscow to find a solution to the crisis in the Balkans, Mr Cook took to the Internet to broadcast his message to the Serb people.

"President Milosevic now faces a simple choice," the foreign secretary writes on the Foreign and Commonwealth Office Website, in an article also available in Serbian.

"He can continue to fight. But he knows that time is on Nato's side. Every day of this conflict weakens his war machine still further.

"The men doing the ethnic cleansing in Kosovo no longer have cover from the air. They are running low on fuel.

"Their morale is crumbling. Russia is fast losing patience with Milosevic. No wonder than more than half of the Serbs who got call-up papers didn't even bother responding!"

Earlier, at a Ministry of Defence briefing, Mr Cook said hundreds of soldiers were deserting the Serb army every week, while fresh conscripts had to be press-ganged to join.

"We have had a number of reports of Serb soldiers trying to withdraw and the special police forcing them back to the frontline," he said.

"Remember most of the squadies in the Serb army are one-year conscripts with very poor training."

Chief of the Defence Staff General Sir Charles Guthrie detailed the impact of Nato's bombing campaign on its 34th day.

Cook defends TV attacks

At the briefing, Mr Cook said he was confident the United States would sign up to the oil embargo of Serbia and defended Nato's attacks on television stations.

Nato strikes have targeted Serb TV transmitters

"I'm quite sure that the Americans will seek to uphold the oil embargo," he said. "I do not think for one minute that Americans will be supplying oil to Yugoslavia while their pilots are trying to bomb Yugoslavia."

He justified the bombing of Serbian broadcasting apparatus, which again came under fire on Monday night, describing it as an integral part of President Slobodan Milosevic's war machine.

"The truth is feared as much as bombs by the Serb government," the foreign secretary said.

"President Milosevic has a long history of suppressing media, of making TV and radio a family business and feeding his people lies."

Russian 'anger and outrage'

Robin Cook: No invasion is planned

Earlier, Mr Cook restated Nato's position that no armed invasion of Kosovo will take place against organised Serb resistance.

Responding to remarks from Vladimir Andreyev of the Russian Embassy in London that a Nato invasion of Kosovo could push Russia "too far", Mr Cook said: "We are not planning an armed invasion of Kosovo against organised resistance from the Serb army."

The UK foreign secretary said Moscow had long known of Nato's intention to use ground troops to secure the eventual peace in Kosovo and allow the hundreds of thousands of refugees to return to their homes.

He added that he hoped Russia "would be there with us".

Vladimir Andreyev: Stop the bombing and resume talks

But Mr Andreyev said "anger and outrage" still existed in Moscow over Nato's strikes against Serbia.

He hoped a diplomatic solution could be found to the problem and urged Nato to "stop the bombing and resume talks".

Relations between Russia and Nato have become strained as Nato plans for an oil embargo against Serbia clash with the Russians' insistence that they will continue to ship oil to the Serbs.