Manchester United have insisted they may report Real Madrid to FIFA over their public pursuit of Cristiano Ronaldo.
The Premier League and European champions have issued a statement describing their 'growing irritation' at continuing comments seemingly emerging from the Spanish club concerning their interest in the Portugal winger.
The statement, released on their website, www.manutd.com, read: 'Manchester United has watched with growing irritation the comments attributed to Real Madrid over their alleged desire to sign Cristiano Ronaldo.
'The facts are: the player is on a long-term contract and his registration is held by Manchester United; the player is not for sale.
'The club will have no alternative but to report Real Madrid to the world governing body, FIFA, if it continues to behave in this totally unacceptable fashion.
'These public attempts to unsettle the player are completely against the regulations and the club will not tolerate them any longer.
'In addition, the club is certain that they are a distraction for the Portuguese national squad as they prepare for the European Championships.
'No one should be in any doubt that Manchester United will do everything in its power to keep its best players.'
That statement came after Madrid coach Bernd Schuster confirmed Ronaldo is his club's number one summer transfer target.
United boss Sir Alex Ferguson has already voiced his dislike of Madrid touting for Ronaldo, pointing out their major domestic rivals, Barcelona, refrain from public expressions of admiration for other clubs' players.
Ferguson accused the Spanish club of lacking morals last week and is now sure to have been further infuriated by Schuster comments almost referring to the 23-year-old's signing as a done deal.
'There are other players we have been looking at but everything has slowed down a little due to all this Cristiano Ronaldo business, seeing as he is the big priority for the club,' said Schuster.
'The English way has been a perfect education for a player with such exceptional individual talent.
'There he has learned to enjoy his football as a complete professional. This means we would get a Cristiano who would arrive here with his lessons learned.'
Real president Ramon Calderon has responded to United's statement by insisting the Primera Liga champions are not trying to unsettle Ronaldo.
Calderon is adamant his club have acted correctly and said: 'We haven't interfered in Manchester United's contractual agreement with Cristiano Ronaldo.
'It is a shame that Manchester, a club with which we have excellent relations, is annoyed, because Real Madrid have nothing to do with that aspect.'
Calderon also claimed Madrid have not been in contact with the player.
'Real Madrid have never negotiated with players under contract and we will not do that, because we wouldn't like it if others did it with our players,' he said.
Calderon believes his side's pursuit of Ronaldo has been blown out of proportion by the Spanish and English press.
'The media have fed this problem and we are not going to get into a conflict with Manchester, who are a club we consider to be our friend, and one with which we hope to continue enjoying a good relationship,' added Calderon, who revealed he hopes to speak to United chief executive David Gill to clear up the matter.
'I am going to personally speak with David Gill because I want to clear this up with him and assure him that we are not going to influence any player to break a contractual relationship.
'There is no 'Ronaldo case' and I regret, in the name of Real Madrid, any discomfort this may have caused.
'Our posture in this case is the same as the rest of the teams when there are players under contract.'
However, the 57-year-old did not rule out signing the United forward at some point in the future.
'If the team decides to sell the player, that's another thing,' he said. 'What is occurring is a problem between the player and his team.'
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