Bayern Munich chairman Karl-Heinz Rummenigge is ready to report Manchester United to FIFA if the Premiership club continues to pursue Owen Hargreaves.
United boss Sir Alex Ferguson has made no secret of his desire to sign the England midfielder, who has told the Bundesliga champions he wants to move to Old Trafford.
Bayern made it clear last week that Hargreaves is not for sale and Rummenigge is now ready to take action to bring the saga to an end.
"We have told Manchester United to drop their interest, or we will have to turn to FIFA," he told the Tz newspaper.
"A club can only contact a player when the club, who owns the player's registration, is in agreement.
"We are not Hamburg, who let Khalid Boulahrouz go [to Chelsea] at the first sign he wants out. We are FC Bayern.
"We do not just let anybody go - the employer decides here, not the employee."