Bayern Munich have insisted Thomas Müller is not for sale after a report in Sport-Bild claimed Manchester United had made an official €85m (£60m) bid for the forward last week.

United’s interest in Müller is well known but there has yet to be any confirmation from the club of a firm offer.

Matthias Sammer, Bayern’s sporting director, said: “It is not Thomas who is causing the fuss, it is his performances. And we can’t do anything about that. [Chief executive] Karl-Heinz Rummenigge is right, he is a player that we cannot put a price on.”

United are aware of the German club’s stance yet Louis van Gaal is keen to test Bayern’s resolve. Earlier in the summer United made informal contact regarding Müller but were told he was not available. At the time, Rummenigge promised supporters that Bastian Schweinsteiger, who was bought by United in July, would be the only Bayern player sold to the club in this transfer window.

Bayern are aware, though, that Müller is flattered by Van Gaal’s desire to buy him and the United manager’s strategy may be to force Rummenigge into a public acknowledgment that there has been an official offer. United are also aware that by making their interest clear this summer, they may stand a better chance of getting their man in a year’s time.

Rummenigge would find it difficult politically to sell Müller, at least this summer. In last Friday’s Bundesliga opening match the striker scored twice against Hamburg at the Allianz Arena.