Roy Keane: Double charge (AntonWant/Empics)

The 31-year-old Manchester United skipper has previously indicated he would fight the charges, which both centre around allegations made in his recently-released autobiography.

An FA statement confirmed: 'Further to requests from Roy Keane, the Football Association can confirm they have agreed a 48-hour extension to the deadline in which the player has to respond to the two FA charges he faces.'

Keane is facing at least another month on the sidelines after undergoing a knee operation which could coincide with any ban he might face.

In his book, Keane claimed he had deliberately set out to injure Manchester City midfielder Alfie Haaland during the derby match at Old Trafford in April last year.

The FA have charged Keane with deliberately setting out to injure an opponent and also that he has profited from his revelations.

Apart from a hefty fine, the United captain is also facing the prospect of an eight-match ban.

The FA have informed Keane`s club about the change to the deadline, adding: 'Manchester United have been made aware of this information. It is not unusual in disciplinary cases for extensions to be granted for players to respond. In this case it is now 5pm on Friday.'

In his book, Keane stated: 'I'd waited almost 180 minutes for Alfie. I'd waited long enough. I hit him hard. The ball was there (I think). Take that.'

Haaland has not played a full game since the incident and is still considering taking legal action against Keane, as are Northern Irish outfit Linfield, who were outraged by comments made against them in the controversial autobiography, which has attracted widespread condemnation.

Professional Footballers' Association chief executive Gordon Taylor has already admitted Keane has left himself open to disciplinary action over his comments, while former Old Trafford and Republic team-mate Denis Irwin is among those who has expressed surprise that the book was not released once Keane's career was over.

Keane did little to quell the controversy in a series of interviews to coincide with the release of the book, insisting it was 'an honest account' he had read and was happy with.

However, he subsequently back-tracked slightly, claiming ghost-writer Eamonn Dunphy had incorrectly paraphrased his comments.

There has also been the suggestion Keane may appeal on freedom of speech grounds, although the Irishman's camp have remained silent on that issue.

It is thought United boss Sir Alex Ferguson was the only member of the Old Trafford staff to read a transcript of the autobiography before its release and since the row erupted, United have sought to 'discourage' any more members of their staff, including Ferguson himself, from penning their memoirs.

Last week Ferguson defended the decision to send Keane for his operation, which it was initially feared would keep him out for three months.

'Why people should be so up in arms at the decision to let him have his hip operation during his suspension period I really don't know,' he said.

'He needs to have it done and this is a good opportunity. Would any manager seriously let a player serve a suspension and then send him into hospital?'