Schalke general manager Horst Heldt has told any interested clubs they must pay up for young gun Julian Draxler.
The 21-year-old winger remains a target for Arsenal, who have been admirers for some time, while Tuttosport claims Manchester United are also keen.
Schalke are aware of the interest in their promising German international, prompting Heldt to suggest to anybody wanting to buy Draxler that he will not come cheap.
"Our plan is not to sell Julian," Heldt told the Rheinischen Post.
"That said, in this business it's difficult to make definitive statements.
"If another club makes an astronomical offer for a player, for the good of the club you must always at least consider it.
"We want to keep him, but we can only definitively put the issue to bed on August 31. To say anything else would not be honest.
"Today I could say 'he will not leave', but then a few days later a huge offer for him is put on the table."