Manchester United manager Sir Alex Ferguson has revealed that striker Wayne Rooney will miss another two weeks due to a knee injury.

Rooney sustained the problem in training on Christmas Day and had originally been scheduled to return in time for United's FA Cup third-round match with West Ham on Saturday.

However, Ferguson has now confirmed that Rooney will be held out for a further two weeks, meaning he will miss not only the West Ham match on Saturday but also a league meeting with Liverpool on Jan. 13.

"It's not serious but it's going to take longer than we thought," Ferguson said on Friday. "It's probably going to be another two weeks. He won't be fit for Liverpool.

"It's a surprise as he was meant to be back training now. So he'll be out for longer than we thought."