After 78 days of bombing, Nato has begun to mobilise K-For, its international intervention force, following the peace agreement reached this week.

The Ministry of Defence (MoD) has given limited details on the UK's contribution, which stands at 13,000 troops to be active in Kosovo, with 6,000 on standby. The MoD estimates there are about 8,500 troops currently in the Balkans.

The BBC's Kate Adie: "It is not simply a matter of national pride"

Prime Minister Tony Blair has sent a message of support to the British forces, telling them how proud he is of them.

"My message first of all is one of gratitude because the British forces have been quite magnificent," he told the British Forces Broadcasting Service, which has stations across the Balkans.

He also acknowledged the hazards they face as Operation Joint Guardian begins, but added: "We are going in for a right and just cause, and when those refugees are allowed back into their homeland, it will be in no small measure due to the bravery and dedication of British forces."

Lieutenant-General Sir Mike Jackson has ordered his Nato forces to deal with both Yugoslav and KLA units in an "even-handed" manner, underlining that all civilians must be protected.

'Security and safety'

As the Serb withdrawal of troops from Kosovo continues, Armed Forces Minister Doug Henderson said he wanted to make it clear there would be "no gung ho-ism and impatience on the part of Nato's troops".

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Stressing the success of Nato's air campaign against Serb troops, he said: "The troops will be measured, thorough and impartial, operating with the highest standards of security and safety for the population of Kosovo."

Three tasks

He said it would be a "tough and dangerous job" for Nato's troops, with three main tasks:

• 1. To see that all Serb forces withdraw in accordance with the agreement
  

• 2. To ensure that "peace means peace" - the new force must be quickly installed
  

• 3. To take stock of what they find and assess the impact of the crisis. Mines laid by the Serb troops are a major problem, and they must be identified and cleared. Aid agencies will help provide "life-supporting facilities" for the Kosovo Albanians

Major Marshall Sir John Day, the Deputy Chief of Defence Staff, said that while Nato had achieved air superiority early in the campaign, it was now over to the ground forces to finish the job.

He said that Serbia had lost about one third of its military aircraft.