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Franck Ribery: Bundesliga star

The Guardian report that United made the offer some weeks ago after club scouts repeatedly watched the 26-year-old in action.

The offer, which would smash the current world record transfer of £44m set in 2001 when Real Madrid signed Zinedine Zidane from Juventus, would only come into effect if Ronaldo leaves for the Bernabeu.

While the paper contends that the Portuguese star is almost certain to leave, earlier this week the World Player of the Year said: "I'm no longer thinking of Madrid. That dream is dead," but despite the 24-year-old's comments speculation over his future and links with Madrid are inevitable given his standing in the game.

Although Bayern are understood to have turned down United's offer it could regarded as an opening gambit in negotiations for an increasingly unsettled player who has no shortage of suitors, with Barcelona and Manchester City already linked with summer bids.

Ribery has grown increasingly discontented at the Bundesliga club this season and last week said that he might have to leave unless the club can secure Champions League football next season.

Only Germany's top two teams are guaranteed places in the Champions League and while Bayern are currently second three points off behind leaders VfL Wolfsburg Hertha Berlin, Vfb Stuttgart and Hamburg are keeping the pressure on Bayern.

The former Marseille player, who moved to Munich in 2007 and is contracted to Bayern until 2011, has so far rejected the chance to begin talks over a new contract.

Over the weekend Bayern were linked a move for Werder Bremen's Brazilian playmakerDiego, with general manager Uli Hoeness quoted in the Suddeutsche Zeitung newspaper saying Diego "becomes an issue for us if Ribery actually leaves." In response Werder director of sport Klaus Allofs admitted: "I cannot say that we will not be selling any player because somebody may come in with a gigantic offer," said Allofs. "If Bayern were to call, then I would not hang up."

Italian giants Juventus have already made contact with Bremen about Diego, while Serie A rivals Inter Milan are also thought to be keen on the attacking midfielder.