Roger Federer
Roger Federer still to make a final decision on clay competitions this year. Getty

Roger Federer has not yet decided if he will have a clay court season in 2018 but says he will not commit to any events unless he feels "100%".

Last year, Federer opted against competing on clay in order to prolong a professional career which has now entered its 20th year. It was a decision that paid off; after winning his first grand slam title in five years at the Australian Open, the Swiss went onto win Wimbledon for the eighth time.

Federer's name was conspicuous by its absence as Monte-Carlo Masters tournament director Zeljko Franulovic listed Rafael Nadal, Novak Djokovic and Stan Wawrinka among the main attractions of this year's competition in the spring.

It could be one of the many events the 36-year-old passes on, with Federer admitting an intense season on clay is not part of his plans this year.

"The clay season is up in the air. If I am playing a lot during this part of the season it would be hard to play a robust clay season. It would be a light [schedule] if I do play," Federer said, AFP report.

"We will see how it goes. I am healthy and glad to be playing. I should be playing when I feel that way and not play when I don't feel at 100 percent or don't feel ready to do it. That is my secret for me moving forward."

Federer's immediate focus is on reclaiming the number one ranking. The 20-time grand slam winner only has to reach the semi-final stages of the Rotterdam Open this week to return to the summit of the sport, with current number one Nadal sidelined with a hip problem.

If he can reclaim top spot, he will extend his record for most weeks at the top of the rankings, which currently stands at 302, while he will also replace Andre Agassi as the world's oldest world No.1, a record the American held when he was 33.