After a vigorous exchange of views during a private meeting with Bill Clinton, the Russian president cut short a meeting with the German and French leaders after less than 10 minutes.

His spokesman Dmitri Yakushkin told reporters the decision was connected to a decision to delay until Friday the signing of a new European Security Charter.

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"Since there is no signing ceremony today, we have decided to leave a bit earlier. We are leaving directly now," Mr Yakushkin said.

Western countries postponed the signing of the Charter because of disagreements with Russia over references to Chechnya in the final summit declaration.

However, by Thursday night Western diplomats said an agreement had been reached, and the way was open for the signing of the Charter on Friday.

Kremlin spokesman Dmitry Yakushkin said Yeltsin had returned to Moscow "in a good mood".

And Foreign Minister Igor Ivanov said he believed Yeltsin had managed to win sympathy for Russia's position

Political solution

Russia had wanted no mention in the declaration of what it says is an internal matter, while Western diplomats reportedly wanted a reference to the need for protection of civilians and proportionate use of force.

After talks between the foreign ministers of Russia, Germany, the UK, France and Italy, German foreign ministry spokesman Andreas Michaelis said that the declaration would include a call for a political solution to the Chechen crisis.

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He added that Russia would express its readiness to invite the chairman of the OSCE to visit the region, and the mandate of an existing OSCE mission to Chechnya would be reaffirmed.

The OSCE mission helped mediate an end to the first Chechen war in 1996 but has since been barred by Russia from entering the breakaway republic, and Russia has rejected all offers of third party mediation.

Boris Yeltsin was in jovial mood before the opening of the summit

The French president's spokeswoman said Mr Schroeder and Mr Chirac were visibly surprised by the abrupt end to their meeting with Mr Yeltsin.

However, she said, they had agreed to meet again in Paris on December 21.

Earlier, Mr Schroeder told the opening session of the Organization for Security and Co-operation summit that war was not the way to eliminate terrorism.

"The massive use of force which hits the civilian population before all else must be ended," he said.

President Clinton, who spoke shortly afterwards, said he supported Mr Schroeder's words, and he warned that Russia's actions could increase rather than reduce the threat of terrorism, and result in an endless cycle of violence.

He rejected Mr Yeltsin's argument that Chechnya was a purely internal affair for Russia.

"President Yeltsin, one of the most thrilling experiences of my life ... was when you stood up on that tank in Moscow when they tried to take the freedom of the Russian people away," he said.

"If they had put you in jail instead of electing you president, I would hope that every leader of every country around this table would have stood up for you and for freedom in Russia and not said, 'Well that is an internal Russian affair that we cannot be a part of'."

"There must be a political dialogue and a political settlement," he said.

Boris Yeltsin said the Russian army's offensive in the rebel republic was a fight against international terrorists, whose aim was to spread extremism throughout the world.

He was unapologetic about the scale of the assault.

"We do not accept the advice of so-called objective critics of Russia," he said.

"Those people do not understand that we simply must stop the spread of this cancer and prevent its growths from spreading across the world."

He said there could be no negotiations with bandits, and that peace required their "complete destruction".

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The two men subsequently held an hour-long bilateral meeting, after which Mr Clinton said they had failed to resolve their disagreement over Chechnya.

As Mr Yeltsin addressed the summit, Russian troops continued their advance towards Chechnya's capital Grozny, capturing the south-western town of Achkoi-Martan.

The head of the UN refugee agency, Sadako Ogata, was visiting the north Caucasus to see for herself the suffering of some 200,000 refugees who have fled the bombardment of their villages in Chechnya.

Apart from the Security Charter, the Istanbul meeting is aiming to tie up a revised version of the 1990 Conventional Forces in Europe (CFE) treaty.

The new CFE accord will cut by an average 10% the ceilings established in 1990 for deployment of weapons such as tanks, aircraft and artillery forces, notably on front lines between the former enemy blocs.