Federer has been suffering from a viral infection

The Swiss star, 26, was beaten in the first round of last week's Dubai Championships by Britain's Andy Murray.

That defeat was Federer's first match since losing to Novak Djokovic in the Australian Open semi-finals in January.

Federer said: "In Switzerland there is a little too much speculation my career is over. But I am happy and healthy, not miserable and down and out."

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

606: DEBATE Will Federer overtake Sampras's record?

He has since been given the all-clear to play and battled to a 6-3 6-7 (7-4) 7-6 (8-6) victory against 14-time Grand Slam winner Pete Sampras in an exciting exhibition match at Madison Square Garden on Monday.

Sampras displayed his trademark serve-and-volley game, improving with each set and prompting Federer to step up in order to secure victory in two hours and 15 minutes.

Federer will now compete at the Pacific Life Open at Indian Wells, California later this week.

He is within two Grand Slam titles of Sampras's record haul of 14, and insisted that he would use his recent defeats as motivation to complete the feat.

"Honestly, losses like this motivate me more than anything," he added.

"Trying to come back, trying to prove I'm still the one to beat. I just want to show I can do it over and over again.

"I love competing on centre courts all over the world. So many people are happy when I get there. It touches me. I love to practice more and more now," he said.

When it comes down to it at the big, big events, I think he'll be the guy standing with the trophy Pete Sampras

"What I enjoy most are the matches, the pressure, the fans, centre court. I hope that's going to stay with me as long as possible."

Sampras also played down suggestions that Federer's dominance was on the wane.

"In a lot of ways Roger has created this sort of monster of being unbeatable," said the 36-year-old American.

"If you lose a match here, lose a match there, people have the assumption he has lost his edge, lost his dominance. I don't look at it like that at all.

"He'll play Indian Wells and he'll play Miami (in two weeks) and do fine at those events. When it comes down to it at the big, big events, I think he'll be the guy standing with the trophy."