When Russian President Boris Yeltsin sat down for an hour-long chat this afternoon with President Clinton, he handed over an extraordinary gift -- a thick file of declassified KGB documents about the assassination of John F. Kennedy.

Samuel R. "Sandy" Berger, the White House national security adviser, called the stack of papers "a very interesting gift" that will be scrutinized, translated and eventually released to the public. He said it was the fruit of Yeltsin's command, issued several years ago, that Russian agencies should review all information related to Kennedy's death, including any secret files on his accused killer Lee Harvey Oswald, who lived briefly in the Soviet Union.

Yeltsin's goodwill gesture helped break the ice in U.S.-Russian relations and set a conciliatory tone for his 17th meeting with Clinton, which Berger described as "one of the best." After weeks of hostility over NATO's bombing campaign against Yugoslavia, Yeltsin said he wanted to bury the hatchet with his counterparts from the seven major industrial democracies and start repairing ties between Moscow and the West.

"The most important thing is to mend ties after a fight," Yeltsin said upon his arrival here for the concluding day of the Group of Eight summit. As he enveloped his host, German Chancellor Gerhard Schroeder, in a bear hug and beamed in the company of British Prime Minister Tony Blair and French President Jacques Chirac, Yeltsin said, "I am among my friends now," according to those present.

Yeltsin, who struggled gamely to display some vigor despite obvious signs of poor health, said he was eager to revive the U.S.-Russian dialogue that had been so disrupted by the Kosovo crisis. He invited Clinton to visit Moscow at the earliest opportunity, and the two agreed to resume sorting out their differences over nuclear arms control and ballistic missile treaties in the fall.

Other leaders greeted the offer of renewed friendship with the West with surprise and relief. Blair spoke of a new "bridge of understanding" being built with Russia and said all the summit leaders were impressed by Yeltsin's message that it was time to seek a fresh start on peaceful cooperation rather than dwell on the animosities that surfaced in the Kosovo conflict.

"There was a very, very good feeling around the table about him and about the future," Blair said. "We know we have been through difficulties, but there is a genuine coming together now."

The Cologne trip was Yeltsin's first trip abroad since he traveled to Jordan in February for King Hussein's funeral.

During his eight-hour visit today, Yeltsin walked stiffly, at times tottering as he tried to keep his balance, and his face and body looked bloated. But Berger said that during his talk with Clinton, Yeltsin looked robust and seemed in good humor.

"I thought he was very much in charge," Berger said. "He was very forceful, and his fist was pounding at a couple of points."

Canadian Prime Minister Jean Chretien, who engaged in a bit of playful arm-wrestling with Yeltsin as the eight leaders gathered at the table for their final session, said the Russian president's health did not seem as precarious as it had appeared on other occasions.

"He appeared physically strong," Chretien said. "He can't run a marathon, but he is in good form."