Federer has only played two tournaments in 2008

The 26-year-old Swiss lost in the first round in Dubai last week, having been beaten in the Australian Open semi-finals in his previous match.

Federer fell ill after his shock loss in Melbourne and was diagnosed with mononucleosis, a virus causing fevers, sore throat and swollen lymph glands.

He has now been given the green light to resume practising "at 100%".

606: DEBATE It would be in his best interests for his health to take some time off to fully recover modernhappygill

"The doctors said I must have had it for at least six weeks, which went all the way back to December," said Federer.

"When I heard it was 'mono', I was actually even more happy to have made the semi-finals of the Australian Open because probably a doctor would have said: 'You're not allowed or can't play'."

He added: "I finally have the green light and finally I can give 100% in practice again, because it wasn't fun sort of being there sort of halfway.

"Through a career, a long career maybe as number one, you have to go through injuries and sicknesses."

Speaking to the New York Times, Federer also explained his criticism of Andy Murray's style of play after losing to the Scot in Dubai.

Federer said he was only trying to provide "constructive criticism".

"He beat me after all," said Federer. "It's unfortunate, because that's not what I meant at all."

He added: "I've always thought he was one of the most talented ones of the whole group, even more talented than (Novak) Djokovic, to be honest.

"I thought he would do the most first before Djokovic, but Djokovic played really well the last year and started this year unbelievably."