The surgery was revealed by the agent who helped engineer Saha's 12.8-million-pound move from Fulham, Ranko Stojic, who claimed his former client would be out until at least November.

"Louis has had surgery in America and he won't be on the field now for a few months," Stojic told Tuesday's edition of the Manchester Evening News.

"I don't know when he will be able to start training again but he is looking at being back around November or December. But it is going to be a while."

A spokesman for the Stellar Group, which has represented the player since the end of last year, confirmed the surgery but insisted Saha was on track to be fit for the start of next season in August, claiming Stojic had no authority to speak on behalf of the Frenchman.

Injuries are a sensitive subject for Saha as United boss Sir Alex Ferguson has made no secret of his frustration with the amount of time he spends in the treatment room.

United have already moved to bolster their attacking options for next season by signing Portugal winger Nani and agreeing terms with FC Porto for their Brazilian playmaker Anderson.

England forward Alan Smith meanwhile appears to be moving towards the exit door at Old Trafford after failing to break into the first team since making his comeback from a year-long injury lay-off.

In comments to the Sun newspaper, Smith hinted that he had become frustrated with the uncertainty over his future.

"If they are going to sell me, I'd like to know," Smith was quoted as saying. "But I won't find out unless I get to speak to the manager."

Smith was a seven-million-pound signing from Leeds two years ago and has two years left on his current deal, but United have made no move to extend that contract.

Tottenham, Aston Villa and Rangers are among clubs believed to be monitoring Smith's situation.