Roger Federer has withdrawn from next week's Stockholm Open saying he needs to rest before starting his quest to reclaim the top spot in the world tennis rankings.
The Swiss world No.2 said in a statement on his website on Wednesday that he had been playing catch-up all year after being diagnosed with mononucleosis at the start of 2008.
"I feel fortunate to be healthy again, but I want to remain at the top of the game for many more years to come and go after the No. 1 ranking again," Federer said.
"In order to do that, I need to get a proper rest and get strong again so that I am 100 per cent fit for the remainder of the year or next year. At this point, I am not sure when I will be ready to play again, but I hope to be back at some point before the end of the year."
Federer apologised to fans who had hoped to see him play in the Swedish tournament, which starts on Monday at Stockholm's Royal Tennis Hall.
Federer lost the No.1 spot to Rafael Nadal this year after the Spaniard beat Federer in both the French Open and Wimbledon final.