LONDON - Old foes Rafa Nadal and Roger Federer will meet in the group stage of the ATP World Tour finals starting in London on Sunday while world number one Novak Djokovic will clash with number three 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 semi-finals.

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 quarter-finals but lost to the Swiss in Sunday's Paris final.

American Mardy Fish completes the pool despite being troubled with a hamstring strain.  

Spaniard Nadal, who beat long-time rival Federer in the French Open final in June, missed the Paris Masters in order to focus on the World Tour finals -- which includes the eight best players this year.

Djokovic, who has enjoyed a scorching year including winning the Australian Open, Wimbledon and U.S. Open, also pulled out of the Paris Masters because of a sore shoulder but should be fit for the week-long London showpiece.

The Serbian has been drawn in Group A alongside Briton Murray, Spaniard David Ferrer and Czech Tomas Berdych.

Murray's 17-match winning streak was ended by Berdych in the Paris quarter-finals last week.

Tsonga will face Federer for the seventh time this year but is looking forward to the challenge.

"Obviously it couldn't be an easy draw but it's a very good group for me, I'll be playing against Roger once again," the Frenchman told a news conference in Paris.

"I'll play Rafa on a (hardcourt) surface that suits me really well and I'll be expecting to beat Mardy Fish. Having played there three years ago will help me because I won't be looking around telling myself 'oh it's great to be here'. I'm not going there just to participate."