Nikolay Davydenko ended seven years' losing streak against Roger Federer on Saturday, finally beating the world number one 6-2, 4-6, 7-5 to reach the final of the ATP World Tour Finals for a second successive year.

The Russian had lost all 12 of his previous clashes with the Swiss mogul since they first met in 2002 but produced an impressive performance in front of 17,500 fans inside the O2 Arenato hold off a Federer fight back.

He will in the final play U.S. Open champion Juan Martin del Potro who edged past Swede Robin Soderling 6-7(1), 6-3, 7-6(3) in the other semifinal.

Despite the loss, the Swede has captured hearts of the fans in the season-ending tournament as an alternate, beating Rafael Nadal and Novak Djokovic in straight sets in the round-robin phase to win Group B.

"I've played against the very, very best, and I won two matches and lost two," said Soderling. "I think I've showed that I can compete with these guys without playing my best tennis."

Soderling broke Del Potro for the first time to take a 4-2 lead in the third set, but couldn't put the Argentine's surge under control. He hit two straight backhands into the net to allow Del Potro to break right back, and then quickly fell behind 4-0 in the tiebreaker.

"It was so close. The difference was just a couple of points in the tiebreak on the second set. But, anyway, he had a great season. I wish the best for the next one," said Del Potro.

The 25-year-old Soderling will finish the year in the top 10 for the first time, and will enter next season with expectations he's never faced before. But he said he's more concerned with developing more aspects of his game.

"I want to get stronger. I want to get faster. I want to move better," the Swede said. "I want to return better and I want to volley better. If I can do that, things will turn out well."

Federer had been the only player in the current top 10 that Davydenko had failed to beat and it had looked as though all Davydenko's hard work would count for nothing as Federer produced a shot of outstanding audacity to move within two points of victory in the 10th game of the deciding set, but the Russian held his nerve to advance.

"I thank all my family, everybody who support me, wait for this moment, you know when I can beat Federer. I was thinking it may come in 2010 or 2011. But in 2009, end of the season, it's a good feeling." said the Russian "Iron Man".

Davydenko, 28, finished second to Djokovic of Serbia in last year's ATP Tour Finals. He edged out the defending champion with a better sets record in Group B.

After ending his season with a loss, Federer said: "It's disappointing. But not to lose against him; just to lose the semis. Coming so far in a tough group, in a tough tournament, I had hoped to get through to the final and maybe win again."