Bayern Munich have threatened to report Manchester United to Fifa unless they call off their pursuit of Owen Hargreaves.
United have admitted they want to sign the 25-year-old midfielder, who has also confirmed that he would like the move.
Bayern chairman Karl-Heinz Rummenigge has warned United to end their pursuit or “we will turn to Fifa”.
“A club may only contact a player when the club holding his contract agrees to it,” he told German newspaper tz.
The German club’s general manager Uli Hoeness added: “Hargreaves is well advised to keep quiet.
“Otherwise I will get very angry and that will not be good for him. I can’t understand that after two discussions he is still forcing the issue.”
Hargreaves was left put of the Bayern’s side for the Bundesliga match with Bochum on Sunday.
Hoeness added: “He won’t be released under any circumstances. He needs to accept the decisions of those above him and show some respect.”
United manager Sir Alex Ferguson has already admitted that Bayern hold the cards and if they refuse to sell he is powerless to do anything about it.
“We are trying hard but Bayern are proving very stubborn and resistant, which I can understand,” said the United boss.
Hargreaves has been at Bayern since moving to the club from Canada as a 16-year-old in 1997. He is contracted to Bayern until 2010.