The Swiss star booked a place in the last four against Argentine David Nalbandian, who squeezed into his second consecutive Grand Slam semifinal this season after battling to a 6-3, 6-3, 2-6, 6-4 triumph over sixth-seeded Nikolay Davydenko of Russia.

    In the women's side, Czech teenager Nicole Vaidisova pulled off another upset, beating Venus Williams in three sets to earn her first Grand Slam semifinal berth.

    Vaidisova blew a 4-1 lead in the opening set before advancing 6-7 (5-7), 6-1, 6-3 two days after she stunned top-ranked Amelie Mauresmo 6-7 (7-5), 6-1, 6-2.

    The 17-year-old Vaidisova next meets 2004 US Open champion Svetlana Kuznetsova, who recovered from a disastrous start to defeat Russian compatriot Dinara Safina 7-6 (7-5), 6-0.

    Defending champion Justine Henin-Hardenne overcame a shaky first set to overwhelm Germany's Anna-Lena Groenefeld 7-5, 6-2 and book a semifinal date with fellow-Belgian Kim Clijsters, a 7-6, 6-1 victor over former world number one Martina Hingis.

    Clijsters was forced into a first-set tiebreak by Hingis, who lost it 7-5 after 54 minutes.

    The second set turned out to be lop-sided in favor of the powerful Belgian, however, and she wrapped up the match in 76 minutes.

    Three years ago Clijsters reached the final only to be beaten by Henin-Hardene, and in 2001 she finished runner-up to American Jennifer Capriati.

    If she reaches the final she can regain the world number one spot from France's Amelie Mauresmo.

    It was Federer's 26th Grand Slam victory in a row, dating back to when he fell in the semifinals here last year to Rafael Nadal.

    The tall and ambitious Croat pushed at him, but was unable to dominate at the net and frequently found himself at the wrong end of Federer's forehand assaults.

    "I've had a good match," said Federer, who is bidding to become only the third man to hold all four major crowns in a year.

    "I'm very happy because it's never easy to play against Mario, never easy to beat him because of his serve. I'm happy to be in the last four, it was my first goal.

    Federer has yet to play a marathon in his first five matches, which he believes will play to his advantage. If he wins his next match against Nalbandian, he'll likely face Rafael Nadal in the final, who recently beat him in a five-hour classic in Rome.

    "It's definitely going to help because it can sometimes cost you like a tournament or a match if you play a very tough one, then you come out and you can't really feel like you maybe have to shorten the points and stuff and you have to change your tactics because of fatigue," Federer said.

    "That's the worst. I feel like I can back up tough matches now.I got two days now, so I guess fitness won't play a factor any more now." Enditem