In a bout of intense diplomatic activity on Wednesday, he met Nato Secretary General Javier Solana and then the leaders of the European Union in Brussels.

Mr Annan said he was in daily contact with a number of governments and was doing what he could in private to explore any possible scope for a political solution to the crisis.

Correspondents say it is likely that if Nato decides to try to contact Serbian President Slobodan Milosevic, it will do so through Mr Annan.

The UN chief has declared himself ready to travel to Belgrade if necessary.

The alliance may also seek the UN's endorsement for a future international military presence in Kosovo.

Unconditional return of refugees

German proposals for a possible 24-hour pause in the bombing campaign to allow Serbian forces to begin a withdrawal have been greeted cautiously by Nato.

German Chancellor Gerhard Schroder said that air strikes would then be permanently called off when it was clear that all Serb troops had been pulled out of the province.

EU leaders did not discuss the plan. However, they did endorse a UN peace initiative announced last Friday calling on Yugoslavia to withdraw its troops, allow the unconditional return of all refugees and accept an international military force.