Roger Federer goes into the season-ending ATP Tour Finals today determined to finish the year as world No.1.

Federer knows his biggest rival Rafa Nadal will snatch top spot in the rankings if he wins the prestigious event at London’s O2 Arena.

But the Swiss sensation, who has had a stunning year, passing Pete Sampras’ all-time record for Grand Slam singles titles by winning the French Open and Wimbledon crowns, is not going to give up without a fight.

“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,” said Federer, who kicks off his Group A campaign against Spain’s Fernando Verdasco today.

“Definitely I am here to win the tournament and to try to stay number one in the world. It is obvious.

“The competition is really stiff so it is not going to be easy for me or Rafa if he wants to get it. 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.”

While Federer is hungry to remain top of the pile come the end of the year Spanish ace Nadal is less concerned with the rankings.

The 23-year-old says he is just happy to be back to full fitness following a season punctured by injury.

“I feel perfect in all aspects, mentally and physically,” he said. “I will play against the best players in the world so I can lose every match but I can win every game as well.

“For me the main thing is to be here and enjoy this experience. The rest, finishing number one doesn’t matter. My only goal is to try to play my best tennis here in London.

“If I am competitive then I am more than happy. To be number one I have to win the tournament. I can’t lose any matches so for me it is not a real chance.”

Nadal faces Novak Djokovic, Nikolay Davydenko and Robin Soderling in his group.