Switzerland's Martina Hingis has beaten the 1999 US Open champion, Serena Williams, at the Sydney International tennis tournament. Her victory comes after she defeated the Williams sisters in the first round of the women's doubles.

The Swiss star needed 102 minutes on Thursday to fend off the challenge from the younger Williams sister. While the first set only took 42 minutes, the second set saw Hingis fight back from 4-1 down to lead 5-4.

But Williams, in only her third match since October, refused to let her rival close out the match. She fought back to even the score at five-all before Hingis picked up the pace to win the final two games. The match ended 6-4, 7-5.

Hingis, who has not won a grand slam title since the 1999 Australian Open, said her win has given her a major psychological boost before heading to Melbourne.

"I was never really scared of playing them", said Hingis. "I have to defend my position so I shouldn't be scared of anything. I know I can play good tennis."

Hingis will play Spain's Conchita Martinez in the semi-finals.

In the men's tournament, Roger Federer's run ended in the quarterfinals against France's Sebastien Grosjean. The sixth seed defeated the Swiss number two 7-5, 6-4.

His compatriot, George Bastl, was also knocked out in his quarterfinal match, losing to top seed, Magnus Norman. Bastl, who came through the qualifiers, managed to take the second set in a match that ended 6-4 3-6 6-3.

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