Bayern Munich general manager Uli Hoeness has revealed Manchester United have made a 'non-concrete' enquiry for Franck Ribery.
United are among several clubs to have been linked with a bid for Ribery, who still has two years to run on his contract.
Spanish rivals Barcelona and Real Madrid are also rumoured to be keen to sign the France international, although Bayern are confident of keeping hold of the winger.
Reports have claimed that United would look to bring Ribery to Old Trafford in the summer, if Cristiano Ronaldo moves to Real.
Hoeness has confirmed United's interest in Ribery hinges on Ronaldo's future, but would want more than the 40million euros being quoted.
"I would really not even answer the phone if the amount would just be £34m," Hoeness told Sport-Bild.
"There was a casual request from Man Utd. But then it depends on Cristiano Ronaldo."
Hoeness has also been critical of the work ethic of Bastian Schweinsteiger, suggesting the midfielder needs to consider if he wants to stay at Bayern.
He added: "You have to confront him with the question of if he wants to continue to be just one of the boys, if the performances he has showed this term are really what he wants it to be in our team.
"The performances of a couple of players are not like their contracts. We will have to think about the roughness of a potential cut inside the squad."