Mr Annan's move to join EU leaders in Brussels on Wednesday came as Nato reaffirmed its determination to continue the bombing campaign until President Milosevic complied with the demands of the alliance.

During his first official visit to Spain, Mr Annan said he had written a personal letter to Mr Milosevic suggesting face-to-face talks.

"I have not heard from him but I have not given up hope," he told a press conference with Spanish Prime Minister Jose Maria Aznar. "I am a hopeful person."

"I am not in a position to say whether we are going to fight our way in or there may be a surprise for all of us," he added.

"I would not hesitate to talk to President Milosevic if it will help."

UN peace plan

The UN Secretary-General said that the way forward was for Yugoslavia to accept UN proposals for an international rather than a Nato force to oversee the return of ethnic Albanian refugees.

The BBC's Daniel Schweimler in Madrid: "Despite the offer, Mr Annan did not look hopeful"

Nato has demanded that all Yugoslav forces leave Kosovo before it will be prepared to stop the bombing.

Mr Annan added: "The proposals I have put forward did appeal to President Milosevic to allow the refugees to go back in security.

"We can only do that by ensuring that there is a military presence."

Slobodan Milosevic has not replied to the UN chief's letter

Mr Annan said that Russia, which opposes the Nato attacks, had "a constructive role" to play in finding a solution to Kosovo, stressing that it was essential for Moscow and Nato to co-operate.

During a private visit to the Spanish town of Toledo over the weekend Mr Annan stressed: "We are praying for peace and we are searching for a lasting solution that will put an end to the human tragedy, the suffering and destruction.

"I hope we will succeed soon."

The Spanish prime minister, who left after the meeting for talks with President Clinton in Washington, said Spain supported the UN plan.

Meanwhile Spanish defence minister Eduardo Serra said Nato would be prepared to capture President Milosevic and bring him to the Hague to answer charges of war crimes.