Cape Town - Tennis fans are all wondering when Roger Federer will hang up his racket, but the Swiss legend says he still "cannot predict" when he will call it a day.

Federer has been playing professional tennis since 1998 and, at the age of 38, many fear that he could quit any day now.

However, he is still going strong and competing with the best in the business as he finished the year as the world No 3 behind Rafael Nadal and Novak Djokovic.

Federer plays a reduced schedule these days to prolong his career, but he still has energy for exhibition tournaments and he will feature in a few matches in South America this week.

When asked when he will stop playing, he replied: "My retirement will depend on my health. At the moment I do not see any reason to retire.

"I did not think I would play beyond 35, 36 years and here I am. I am doing well physically. I cannot predict when it will be the time to stop.

"I think in 2009 I questioned it for the first time. (It has been) 10 years and here I am. I'm exactly where I wanted to be at this age."

Federer won his 100th singles title in March this year and added another three titles to his collection to leave him on 103, six short of Jimmy Connors record of 109.

"With age everything gets a bit more difficult," he continued. "But at the same time, with experience also you can savour the moments more.

"I don't know how it's going to end. I hope it's just going to be somewhat emotional I guess and nice ... I just hope it's going to be good, the whole process, and not too difficult."