"It will be difficult to settle all political issues, but there is a chance," former Prime Minister Viktor Chernomyrdin told reporters.

"It's not a big chance, but a chance. I think we can't let this pass by."

Mr Chernomyrdin briefed President Yeltsin on Saturday about the five hours of talks he held with Yugoslav President Slobodan Milosevic.

Earlier, Mr Chernomyrdin was quoted as saying a solution was "close", but the recent comments suggest he is less optimistic than he originally appeared.

He insisted that a stop to air strikes was one of the main conditions of its political settlement.

Before leaving Belgrade, he said the talks had made "some progress" and that he had discussed sending some kind of international force into Kosovo under the control of the United Nations.

But he declined to say whether the force under discussion would be armed, or whether it would include Nato troops.

Jacky Rowland in Belgrade: "International presence in Kosovo is proving a major sticking point"

Nato has already rejected earlier Yugoslav proposals that any force should consist of unarmed observers.

BBC Correspondent Jackie Rowland described the Russian envoy as optimistic before his meeting and terse on departure.

'Talks should continue'

A statement released by President Milosevic's office said the two men had agreed that the talks should continue.

The meeting took place after Nato's heaviest raids on Serbia so far - Mr Chernomyrdin's plane was held on the runway for more than an hour before taking off as air raid sirens sounded again.

Mr Chernomyrdin said he would spend two days in Moscow before visiting London and Paris.

He said he hoped the Nato countries would take seriously the progress he had made.

Yugoslav offer rejected

Western leaders rejected a seven-point peace plan said to have been agreed in the Belgrade talks this afternoon saying it fell far short of Western demands because it would not allow an armed peacekeeping force.

The Yugoslav Foreign Ministry spokesman reiterated that only unarmed observers under UN auspices would be allowed into Kosovo.

"It's a UN mission ... so, no force, no occupying soldiers on our soil," Foreign Ministry spokesman Nebojsa Vujovic said.

Earlier Mr Vujovic had appeared to suggest Belgrade might consider an international armed force in Kosovo.

Nato spokesman Jamie Shea said the proposals "do not come close to meeting the demands of the international community".

"They are not worthy of serious consideration," he said.

US Secretary of State Madeleine Albright said the proposals were "not anywhere near serious".

Opposition call

Serbia's main opposition party has urged more flexibilty in the search for peace.

In a statement the Democratic Party said Yugoslavia needed to compromise on the make-up of a Kosovo peace force if the bombing is to be stopped.

And the party's Vice-President, Ljiljana Lucic, referring to Mr Chernomyrdin's mission, said: "We need concrete results from the talks, so that they can be put before the UN Security Council."

There has been a flurry of diplomatic activity this week, most of it centring on Russia and its envoy.