Kim Clijsters [Images] stopped Martina Hingis [Images] in her tracks at the French Open on Tuesday, outhitting the Swiss in a 7-6, 6-1 quarter-final win.

The Belgian also knocked Hingis out of the Australian Open [Images] quarter-finals in January and once again her greater weight of shot counted for more than her opponent's tactical nous.

Czech teenager Nicole Vaidisova dazzled Venus Williams [Images] to storm into her first Grand Slam semi-final with a 6-7, 6-1, 6-3 victory.

She will play Svetlana Kuznetsova [Images] in the last four after the 2004 U.S. Open champion recovered from an atrocious start to beat fellow-Russian Dinara Safina 7-6, 6-0.

On her 23rd birthday twice runner-up Clijsters will face defending champion Justine Henin-Hardenne, who beat German Anna-Lena Groenefeld 7-5, 6-2,  in the semi-finals.

If she wins, she will reclaim the world number one spot from Amelie Mauresmo, beaten by Vaidisova in the previous round.

Henin-Hardenne recovered from a tentative start to set up an all-Belgian battle against the second seed.

Aiming for her third title in four years, the fifth seed trailed 2-0 before finding her feet on a sun-bathed Suzanne Lenglen court.

Having clawed her way back into a 4-3 lead, Henin-Hardenne was again broken in the eighth game by the German 13th seed, who was playing her first Grand Slam quarter-final.

That was as good as it got for Groenefeld who surrendered the set by whacking a wild forehand wide.

Henin-Hardenne pinched six games in succession to move 3-0 ahead in the second set. Groenefeld briefly stopped the run but bowed out after 85 minutes, Henin-Hardenne slapping a forehand winner down the line on her second match point.

Former world number one Hingis, who is back on tour after a three-year career break, was playing for a fifth consecutive day at Roland Garros which endured a rain-hit first week.

The 25-year-old, seeded 12, double-faulted to lose her first service game and trailed 5-2 in the first set. She battled back to force a tiebreak but Clijsters, the U.S. champion, took it 7-5 with a backhand pass.

Hingis, who won a title for the first time since her comeback in Rome last month, faded away in the second set under a barrage of winners.

Clijsters needed only 22 minutes to wrap it up, sealing victory when Hingis mishit a backhand long.

"I knew I had to improve my game and step it up a level," said Clijsters. "It was very close (in the first set) and a lot of fun to be out there today."

Vaidisova's win mirrored her shock quarter-final victory over top seed Mauresmo when she also lost a tiebreak before dominating the next two sets.

The German-born Czech turned 17 only in April and if she wins the title she will become the second youngest winner of the French Open behind Monica Seles [Images], who was 16 when she won the claycourt grand slam in 1990.

"I'm so excited I could just scream now," gasped the teenager, whose best previous run at a Grand Slam was reaching the U.S. Open fourth round last year.

FELT RIDICULOUS

A product of the Nick Bollettieri academy in Florida [Images], Vaidisova was able to match the fearsome power of 2002 runner-up Williams, the reigning Wimbledon [Images] champion, and should have won the first set when she led 4-1 and then 5-2 in the tiebreak.

An errant forehand gave it to Williams but, as against Mauresmo, the setback merely spurred Vaidisova on.

She ran through the second set and dominated the third, sealing victory when Williams slugged a forehand long.

Safina had upset another Russian Maria Sharapova [Images] in the fourth round and raced into a 5-1 lead against Kuznetsova who could barely put a ball in court early on.

"I was just playing disgusting points," said Kuznetsova. "I looked like junior out there. I mean, I felt ridiculous."

The eighth seed fought her way back, however, and took the tiebreak 7-5. The second set lasted only 20 minutes as Kuznetsova ran Safina ragged and a big first serve on her first match point clinched her victory.

Later on Tuesday men's top seed Roger Federer [Images] plays Croatian Mario Ancic in the quarter-finals. Argentine third seed David Nalbandian takes on Russia's [Images] Nikolay Davydenko in the day's other men's last-eight clash.

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