Rooney accepted a charge of using 'offensive, insulting or abusive language' following his foul-mouthed outburst into a television camera during last Saturday's 4-2 win at West Ham.
Rood gesture: The United man swears into the camera after completing his hat-trick at West Ham
But he has contested the automatic two-match ban that would rule him out of Saturday's Barclays Premier League clash with Fulham and the Wembley showpiece against Manchester City a week later.
United have submitted Rooney's defence, which will be heard by a three-man independent regulatory commission at Wembley this afternoon.
They claim the punishment is excessive and will point to the fact that Rooney has accepted the charge and issued an apology shortly after the game, admitting he had been in the wrong.
They are hopeful that the England striker - who scored a spectacular winner when United and City met at Old Trafford in February - will have his suspension halved and be available to play at Wembley, although there is a slight risk it could instead be increased.
Wayne's World: Rooney accepted a charge of using 'offensive, insulting or abusive language'
The announcement of the panel's decision could be delayed until tomorrow so as not to interfere with United's Champions League quarter-final against Chelsea at Stamford Bridge tonight.
Rooney should be fit for the tie, despite having treatment on a bruised shin, which conveniently kept him away from the cameras when United trained at Carrington yesterday morning before catching a train to London.
Frank Lampard last night warned Chelsea to beware of a backlash from his England team-mate. He said: 'He's a competitive character. When you get headlines, positive or negative, it can spur you on in different ways. 'He's a fantastic player. He's a top player and he'll be a threat.'
United boss Sir Alex Ferguson said little when he met the media at Lord's cricket ground last night. He said: 'I'm not going to discuss it at all. He missed the training this morning for a good part of it. He was having treatment. I'm sure he'll be fit for tomorrow.'
Facing the music: Ferguson refused to answer questions on Rooney ahead of the Champions League tie
Asked about his striker's frame of mind, the manager added: 'I'm not here to talk about that.' But Chelsea boss Carlo Ancelotti backed Rooney, claiming the striker had been harshly treated. Ancelotti said: 'Obviously the behaviour is not so good, but when you score a goal in Italy nothing happens if a player shouts into a camera.'Here, two-game ban. They are very strong here. I am surprised by this.'
Earlier, the PFA warned on its website that the charge could set a dangerous precedent, with chief executive Gordon Taylor suggesting the FA were making an example of Rooney.
He said: 'If sanctions are to be imposed in such circumstances then this has to be done in a balanced and consistent manner, and participants made aware of this fundamental change.'
To be Frank: Lampard expects Rooney to bounce back from the criticism in their Euro clash
The controversy comes at a bad time for Ferguson after an interview appeared in Italy yesterday in which he held up Rooney as a role model for City's wayward striker Mario Balotelli.
The United manager said: 'Rooney was like that, with an explosive character and so much will to do things that he overdid it. Now he is 25 and has matured a lot.'
Ferguson also warned Real Madrid manager Jose Mourinho he will have to wait to replace him as United boss. Scot said: 'I understand his wish to return to England, because here a coach has more freedom than in Spain, without the constant following of the media and radio. 'But it's difficult for me to say when my position will be available.'
Manchester City will have their full quota of fans at Wembley for the FA Cup semi-final with Manchester United after the governing body decided to re-issue the 900 tickets stolen from a Royal Mail van last week. Greater Manchester Police yesterday arrested a 39-year-old man in connection with the theft.
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