The ultimate piece of “bling”, the American equivalent of the FA Cup winner’s medal, slipped into Mr Putin’s pocket when he met several US tycoons, including Robert Kraft, the owner of this year’s Super Bowl champions, the New England Patriots. The two hours of private talks at Konstantinovsky Palace, near St Petersburg, were also attended by top executives from IBM, Intel and Citigroup.

At a press conference, Mr Kraft, who made his fortune in paper products, is said to have been urged by Sanford Weill, the chairman of Citigroup, to show Mr Putin his flashy 2005 Super Bowl ring. The 14-carat white-gold ring, awarded to all members of the winning team, weighs more than four ounces, making it the heaviest so far, and is studded with 124 diamonds arranged to form the team ’s logo and the words “World Champions”.

When Mr Kraft presented the Super Bowl rings to his team two weeks ago, the club boasted: “These rings pack plenty of bling.”

The rings are also avidly sought by collectors. A less lavish Super Bowl ring previously owned by a member of the San Francisco 49ers sold on eBay last year for $49,000 (£27,000).

Russia’s business daily, Kommersant, owned by Mr Putin’s exiled rival Boris Berezovsky, said that Mr Kraft “shyly stuffed something into” Mr Putin’s hand.

“Putin nodded and quickly looked around. But no, he didn’t see anybody watching. Then curiosity took hold over the President of Russia and he started to look at the present,” the newspaper added.

“There was a massive silver ring in his hands. Putin even carefully tried it on, but when he noticed that photo and video cameras were pointing at him, quickly took it off and held it in the fist.”

The New York Sun reported that Mr Kraft did not intend to give Mr Putin the ring and was trying quietly to retrieve it. “No one is accusing either Mr Putin or Mr Kraft of doing anything improper, but rather of being involved in a diamond-studded misunderstanding,” the newspaper said.

“While Mr Kraft thought he was playing show-and-tell, Mr Putin apparently assumed, in error, that Mr Kraft . . . was offering a parting gift to the leader of the world’s largest country.”

Last night Mr Kraft issued a statement acknowledging Mr Putin as the ring’s rightful owner. “At the end of a very productive three-hour business meeting with President Putin, organised by my good friend Sandy Weill, I showed the president my most recent Super Bowl ring,” Mr Kraft said.

“Upon seeing the ring, President Putin, a great and knowledgeable sports fan, was clearly taken with its uniqueness. At that point, I decided to give him the ring as a symbol of the respect and admiration that I have for the Russian people and the leadership of President Putin. It was truly an act of serendipity and one that I am honoured to have experienced. It touched me to see President Putin’s reaction to the ring.”

A Kremlin official said that the ring had been sent to the Kremlin library, where other foreign offerings are kept.

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