Rafael Nadal and Roger Federer will meet in the group stage of the ATP World Tour finals starting in London on Sunday while world No. 1 Novak Djokovic will clash with No. 3 Andy Murray.

The round-robin competition which ends the men's tennis season is made up of two groups of four with the top two from each pool going through to the semifinals.

Defending champion Federer has not won a grand slam singles title this year for the first time since 2002 but has bounced back to form with triumphs in his last two tournaments including last week's Paris Masters.

"Anyone can beat anyone," said Federer before the draw ceremony in London.

"I'm really looking forward to it. It's a strong year."

Nadal and Federer are joined in Group B by Frenchman Jo-Wilfried Tsonga, who beat Federer in this year's Wimbledon quarterfinals but lost to the Swiss in Sunday's Paris final.

American Mardy Fish completes the pool despite being troubled with a hamstring strain. Djokovic pulled out of Paris because of a sore shoulder but should be fit for the London showpiece. The Serbian has been drawn in Group A alongside Murray.