Mr Yeltsin, speaking hours after sacking his Prime Minister, Yevgeny Primakov, and the entire cabinet, said: "Some people obviously aren't understanding our repeated proposals."

Diplomatic Correspondent Barnaby Mason says if Mr Yeltsin is serious, it could destroy any chance of agreement on a UN resolution authorising an international military force in Kosovo.

Bridget Kendall: "The US special envoy flew in to a full-blown political crisis"

Mr Yeltsin's comments came shortly before US Deputy Secretary of State Strobe Talbott met Russia's Kosovo envoy, Viktor Chernomyrdin, for talks on the composition of an international presence in Kosovo and the potential role of the UN.

Mr Chernomyrdin, who has been working for weeks on a diplomatic solution to the Kosovo crisis, returned from a visit to Beijing on Tuesday, saying he had new proposals to make to the United States.

Both sides described Wednesday's talks as helpful, but no new developments were mentioned.

Strobe Talbott: "Talks were intense and constructive."

"There are some points where we do not see eye to eye," Mr Talbott said.

"There are some very serious points where our views, our aspirations and our recommendations converge.

"This extraordinarily intense and, I feel, constructive and serious day that I've spent in Moscow has been devoted to the task of seeing if we can broaden and deepen those areas of convergence."

The Nato Secretary-General, Javier Solana, said he hoped Russia and Nato would continue negotiations and that a UN resolution on Kosovo would be ready soon.

In other rumblings of discontent, the head of the Russian Security Council, Vladimir Putin, said Russia was unhappy playing the role of a courier, merely taking proposals from one country to another.

And Russian Foreign Minister, Igor Ivanov, said that if Nato pursued the line of continuing and extending the bombing campaign, all efforts to search for a political settlement could prove futile.

Apology to China

Nato's other major critic, China, was offered an unconditional apology by German Chancellor Gerhard Schröder and Nato for the bombing of its Belgrade embassy.

Mr Schröder met the Chinese President Jiang Zemin

Mr Schröder - on a one-day visit to Beijing - said: "I think the Chinese leaders have very much understood that I am very, very serious indeed when I express my emotions of compassion, sadness and my feelings of commitment to the families of the victims."

But he said China was resolute in its demand that Nato halt air strikes on Yugoslavia before it would support a peace deal.

"I'm not trying to conceal that there are differences of assessment here," he said.

Mark Laity in Brussels: "The bulk of the attacks are in Kosovo"

His visit - the first by a Nato leader since the bombing - came as the remains of the three people killed in the embassy attack were returned to China.

It is not clear how far Russia and China intend to co-operate with Nato in the search for peace in Kosovo. Both want an end to the bombing, but the United States and other western governments have rejected that unless Belgrade meets their demands.

Milosevic pays tribute

The Yugoslav leader, Slobodan Milosevic, has paid tribute to the many members of the security forces who he said had been killed in the Kosovo conflict.

He gave no exact figure, but correspondents say such a reference to casualties is rare. He spoke of sacrifice and devotion to the homeland, and went on to praise the armed forces for crushing the rebel Kosovo Liberation Army.

The televised statement came as the army said it was continuing its declared pull-out of some troops from Kosovo. It said troops were moving out in small numbers to avoid heavy Nato attacks.

Nato for its part says it can see no evidence of troop movements.

Reports of bombing

Serbian television reports that Nato bombed the city of Nis, the third-largest in Serbia, on Wednesday.

Jacky Rowland in Belgrade: "Heavy casualties in Nis"

The television reports said a number of cluster bombs landed in the centre of the city, in an area where there are schools and houses.

The attacks on the city came as the United Nations Commissioner for Refugees, Mary Robinson, was expected there. According to Serbian officials, she arrived shortly after the bombing.

Mrs Robinson is in Serbia to assess the humanitarian situation in the country as a result of the fighting in Kosovo and the Nato bombing campaign.

The alliance said on Wednesday it had carried out its heaviest attacks so far the previous night.

Nato said its planes attacked bridges and airfields in Serbia, while in Kosovo, tanks and armoured vehicles were destroyed.

• The costs of war and peace
• Fifty days on - how credible is Nato
• Pilots playing 'cat and mouse'
• Nato apologises to Beijing
• Aid agencies prepare for winter