<div><p>Roger Federer admits the prospect of finishing the year as world number one ahead of Rafael Nadal will fuel his bid to win the ATP World Tour Finals in London.</p><p>Federer goes into the Tour Finals, beginning on Sunday at London's O2 Arena, in pole position in the world rankings, but the Wimbledon champion knows Nadal can still snatch back top spot if the Spaniard wins the prestigious end-of-year event.</p><p>Nadal ended Federer's reign as world number one last year before slipping back to second place after a campaign disrupted by the knee injury that forced him to miss Wimbledon.</p><p>Although the rivalry between Federer and Nadal remains friendly enough, the Swiss star is a fierce competitor who relishes his position as tennis's pre-eminent force and he has no intention of surrendering it over the next week.</p><p>"I am aware of it (the race to finish world number one) and I would be lying if I said I was just here to play well," Federer said on Friday.</p><p>"Definitely I am here to win the tournament and to try to stay number one in the world. It is obvious.</p><p>"The competition is really stiff so it is not going to be easy for me or Rafa if he wants to get it.</p><p>"I think it is fun that it is on the line for the last tournament of the season. I will try my best and see where it takes me."</p><p>Federer will face Spain's Fernando Verdasco in his opening Group A match, while British number one Andy Murray and Juan Martin del Potro, who beat the Swiss in September's US Open final, are also in his group.</p><p>Group B features Australian Open champion Nadal, reigning Tour Finals champion Novak Djokovic, Nikolay Davydenko and Sweden's Robin Soderling, who was handed his place when Wimbledon finalist Andy Roddick pulled out through injury earlier this week.</p><p>London is staging the Finals for the first time in the event's 40-year history and Federer has no complaints about returning to the city which holds some of his most treasured tennis memories.</p><p>The 27-year-old, who has won six Wimbledon titles across the English capital at the All-England Club, said: "It's always nice to be back here. Knowing how crazy this part of the world is for tennis, it is going to be a great end to the season."</p><p>While Federer is setting his sights firmly on that number one position, Nadal is less concerned about the rankings.</p><p>The four-time French Open champion has endured the most traumatic year of his career, with his parents' seperation proving a significant distraction before injury denied him the chance to defend his Wimbledon title.</p><p>Now fully fit again Nadal, 23, claims he is just relieved to be able to test himself against the top eight players in the world.</p><p>"For me the main thing is to be here and enjoy this experience," he said. "Playing the tournament in London will be amazing.</p><p>"The rest, finishing number one doesn't matter. My only goal is to try to play my best tennis here in London.</p><p>If I win the tournament it doesn't matter if I am number ten. The ranking is important yes, but not the most important thing for me.</p><p>"For the last five years I was two and one in the rankings, so I have had this experience for a long time.</p><p>"If I am competive to try to win then I am more than happy. If I win this tournament it doesn't matter if I am one, two or three."</p><img src="http://admatch-syndication.mochila.com/images/ad.gif?aid=63860623&bid=informcom" /></div><div id="copyright"><div>

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