Roger Federer [Images] erased the bitter memory of his loss to Tomas Berdych at the Athens Olympics [Images] four years ago when he beat the Czech 6-3, 7-6 on Wednesday to reach the quarter-finals of the men's singles.

The Swiss top seed joined Spain's Rafael Nadal [Images] and Serbian Novak Djokovic [Images] in the last eight after they ended Russian hopes in the men's singles.

Federer survived a second set scare when a rash of double-faults allowed Berdych to forge a 3-0 lead, but the 27-year-old hit back to gain revenge for his shock second-round upset in the Greek capital.

Judging by his reaction after a service winner on match point he clearly sees a first Olympic medal, preferably a gold one, as a consolation prize after a demoralising year in which he lost his Wimbledon [Images] crown to Nadal.

"I know the difficulty of winning a medal here -- winning six matches in seven days, plus doubles. But that's the way it is," Federer, who faces American James Blake next, told reporters before progressing in the doubles with Stanislas Wawrinka.

Nadal, aiming for the gold medal in Beijing [Images] the day before he takes over from Federer as the world number one, defeated Russian Igor Andreev 6-4, 6-2.

"I'm close to my best level," Nadal told reporters, though he later suffered defeat in the doubles alongside Tommy Robredo as the pair lost 6-2, 7-6 to Australians Lleyton Hewitt [Images] and Chris Guccione.

Third seed Djokovic was also impressive in his 7-6, 6-3 defeat of 13th seed Mikhail Youzhny and next meets Frenchman Gael Monfils.

In the women's singles, the Williams sisters are still on course to meet in the final, although Serena was given a real fright by French teenager Alize Cornet, eventually winning 3-6, 6-3, 6-4 after a dreadful opening set in which she was handed a warning for smashing her racket.

Venus, shooting for a third Olympic gold, beat Victoria Azarenka of Belarus 6-3, 6-2 to set up a meeting with home favourite Li Na who became the first Chinese singles quarter-finalist at an Olympics.

Li, who became China's first top 20 singles player two years ago, began timidly against Estonia's Kaia Kanepi but with the crowd roaring her on she won 4-6, 6-2, 6-0.

Not even home support could help Zheng Zie, however, as she bowed out 6-4, 6-3 to Russian sixth seed Dinara Safina who plays new world number Jelena Jankovic in the quarter-finals.

Three Russian are in the last eight of the women's singles, with Elena Demetieva and Vera Zvonareva [Images], a late replacement for Maria Sharapova [Images], also through.

Men's doubles favourites Bob and Mike Bryan of the U.S. are through to the quarter-finals after a straight-sets defeat of Austrians Jurgen Melzer and Julian Knowle.