The burning desire of Kim Clijsters [Images] illuminated New York's midnight hour on Tuesday, and her reward was a place in the US Open semi-finals.

Fourth seed Clijsters overturned a set and 4-2 deficit against Wimbledon champion Venus Williams [Images] to claim a 4-6, 7-5, 6-1 quarter-final victory that she described as the best of her career.

In the last four the in-form Belgian will face Russian top seed Maria Sharapova [Images], who clawed her way to an equally compelling 7-5, 4-6, 6-4 win over compatriot Nadia Petrova.

Men's champion Roger Federer [Images] safely reached the quarter-finals despite the shock of dropping a set against German Nicolas Kiefer, but for the first time the women's singles took the spotlight with its two quarter-finals providing a five-hour slab of spellbinding action.

Clijsters lost four Grand Slam finals before a chronic wrist injury threatened her career in 2004, and was jubilant in her moment of triumph after wearing out Williams in a match that finished 36 minutes into Wednesday morning.

"This definitely means a lot more than any win that I had before my surgery," the 22-year-old said. "I was seeing the ball really well out there. I just kept going for it."

A moody Sharapova repeated her Wimbledon quarter-final victory over Petrova in a ferocious duel to reach the Flushing Meadows semi-finals for the first time.

The 18-year-old Siberian withstood a strong Petrova comeback in a match blighted by dubious line calls. She failed to serve out for victory in the third set at 5-3 but a ripped backhand service return in the next game secured her semi-final place.

"I wasn't fighting out there basically in the second set. It was like I was giving it up," Sharapova said. "But it gives me confidence I can pull out a win like that."

Kiefer, who was the only man to take a set off world number one Federer during Wimbledon, took another off him before bowing, 6-4, 6-7, 6-3, 6-4.

"It's always a strange feeling when that happens," said the Swiss. "Four sets says it all. It was difficult."

Federer remains on course for a semi-final showdown with third seed Lleyton Hewitt [Images], the Australian he thrashed in last year's final, after Hewitt won his fourth round match against Dominik Hrbaty with aplomb.

Before that Federer must beat dangerous Argentine 11th seed David Nalbandian, the 2003 semi-finalist who ousted Italian Davide Sanguinetti, in the quarter-finals. Hewitt will play Finland's Jarkko Nieminen.

Nieminen earlier became the first Finn to reach a Grand Slam quarter-final when he floored Spain's Fernando Verdasco 6-2, 7-6, 6-3.

Kiefer's ability to vary the pace of his shots has often troubled Federer in the past and the Swiss looked uneasy from the start on Arthur Ashe Court.

It was only while facing a moment of real danger, trailing 30-40 at 3-3 in the third set, that Federer roused himself from mediocrity with a wondrous backhand winner to hold serve. He controlled the match thereafter.

The heavily disguised crosscourt winner was reminiscent of the one Federer played in the final game of his four-set struggle against Kiefer in the third round at Wimbledon.

"It was an unbelievable shot," Kiefer said on Tuesday. "The angle was just too good."

FEMININE SIDE

Hewitt, the champion in 2001, hammered Hrbaty 6-1, 6-4, 6-2.

The Australian's only real distraction was the Slovak's dandy pink and black shirt with two holes cut out of the back.

Hewitt is not quite so in touch with his feminine side and said: "I didn't want to lose to a bloke wearing a shirt like that."

His win meant he has reached the quarter-finals at Flushing Meadows six times in a row.

"It's a great record to have here," Hewitt said. "It's not an easy Grand Slam to do well at every year. So it's a huge positive. I love playing in New York."

Unseeded Nieminen, who knocked Andre Agassi [Images] out of the French Open in the first round in May, stretched out on his back to savour his win.

He said: "It's my best achievement. There's not too many Finnish players. I'm very proud to play for my country."

Nalbandian saw off Sanguinetti 4-6, 7-6, 6-4, 6-2 and will face Federer with some confidence, having won five of their previous seven encounters.

• Complete tennis coverage
• All you want to know about Sania Mirza