England captain Michael Vaughan has been ruled out of the Ashes series in Australia later this year with a knee injury.
Vaughan needs to recover fully after having a fourth operation on his right knee on Monday, said the England and Wales Cricket Board (ECB).
"The specialist advises rehabilitation must be taken slowly in order to give the surgery the best chance of success," the ECB said in a statement on Thursday.
"Michael will be targeting a return to cricket early in 2007 with a view to being available for selection for the World Cup."
The World Cup, which is being held in the Caribbean, starts in March. Vaughan led England to victory in the home Ashes series last year.
The Yorkshire batsman has not played for England since returning home early from the tour of India in February. He will miss the home series against Pakistan, which begins next week, and the ICC Champions Trophy in India starting in October.
The ECB said last week Vaughan would be out of action for between four and six months.
Peter Gregory, the ECB's chief medical officer, said in a statement last week: "Our priority now is to safeguard Michael's long-term interests and ensure he can resume his playing career."
Vaughan had surgery on his knee in December and made his comeback for Yorkshire at the end of May. Soreness in the joint prevented him from fielding in a match against Sussex last month.
England begin their defence of the Ashes in the first Test in Brisbane starting on Nov. 23 with all rounder Andrew Flintoff expected to be named skipper for the five-match series in Vaughan's absence.
Andrew Strauss will captain England in the first Pakistan Test starting next Thursday because Flintoff is injured..
- Schedule: Ashes 2006-07
