World number one Justine Henin's 17-match winning streak at the Dubai Championships ended when she was defeated 7-6 7-6 by unseeded Italian Francesca Schiavone in the quarter-finals.

The Belgian top seed made an unusual number of unforced errors as the feisty Italian ran her opponent all over the court and chased every ball.

"She played well but I didn't take the opportunities and wasn't brave enough. She was better than me, as simple as that," four-time Dubai champion Henin said.

Henin said she felt tired after taking three hours to defeat Katarina Srebotnik on Wednesday, so the last thing she wanted was to face an opponent with the terrier-like qualities of Schiavone.

The Italian rallied superbly and executed some astonishing shots on the run.

Henin held just one break point in the first set, at 2-2, but made a forehand error. That proved to be expensive, as she was unable to earn another opportunity and then played a dismal tiebreak, losing it 7-3.

Schiavone then broke to lead 3-2 in the second set by forcing a backhand error, and as Henin continued to struggle the Italian broke again, at love, to lead 5-2.

Schiavone then twice failed to serve out the match, despite holding a match point at 5-4. But Henin once more played a poor tiebreak, losing the last four points as Schiavone took it 7-4.

"I'm not feeling at my best level, that's for sure," said Henin. "I didn't go for the winners. I was playing not to lose the point instead of trying to win a lot of points. That makes a big difference. I had my chances to come back in the second set but I was too short.

"Especially in the tiebreaks I didn't play well at all, and she came to the net and I didn't and that made a big difference.

Every short ball she was in and I didn't do the same, and that really paid off for her."

Schiavone believed she wasn't aggressive enough when leading 5-2.

"At that moment I didn't push hard enough and she kept going because she's so strong," said Schiavone, whose only previous win over a world number one came against Amelie Mauresmo in the Fed Cup.

"Every point you have to beat her. It's like every point is match point. So at the end when I was in the tiebreak I said you push now or you go home, so it's better that you push now. And I did it.

"To beat Justine you have to play very good, at a high level, and I did today. I think for me it is my best win. Maybe she missed some balls, but personally I think I didn't give the possibility and the chance to come up and come up like she does every time."

Schiavone will next play eighth-seeded Russian Elena Dementieva , whose 5-7 6-3 6-3 win was her third victory in three meetings over third seed Ana Ivanovic of Serbia.

Earlier, Svetlana Kuznetsova reached the semi-finals after holding off a strong second set challenge to beat Amelie Mauresmo 6-1 7-6.

Her next opponent will be fourth-seeded Serb Jelena Jankovic, who celebrated her 23rd birthday with the easiest of victories when sixth seed Anna Chakvetadze retired with an injury after losing the opening set 6-1.

Kuznetsova completely dominated the opening set against former champion Mauresmo, serving well and breaking to lead 2-0. Another break, when the umpire over-ruled to give Kuznetsova the point, gave the second seed a 5-1 lead, and she served out the set in just 23 minutes.

Mauresmo attacked far more in the second set, often serve and volleying, but her efforts took some time to bear fruit as Kuznetsova continued to hold the upper hand.

Mauresmo failed to convert two break points to lead 2-0, and then at 2-2 dropped her serve to love when a deep return forced an error. But, with Kuznetsova unable to maintain her level, Mauresmo broke for 3-3 and then again at love to take a 5-3 lead.

In a fiercely contested ninth game, Mauresmo held a set point which Kuznetsova saved with a backhand winner, before the Russian took the game on her third break point.

Kuznetsova then needed six game points to hold for 6-5, before edging the tiebreak 7-4.

"She changed her tactics (in the second set) and started to come in more from the first serve," Kuznetsova said. "She played better, but I was not moving well in the second set. I did more than a few unforced errors, but then I was lucky that I played good in the important moments."

Mauresmo was disappointed with her defeat, and said the game at 5-3 had been crucial.

"She came up with some great shots in that game, and then I didn't play the tiebreak as I expected," Mauresmo said. "Apart from that, I thought I took my chances the way I needed to."

Jankovic dominated the first set against Russian Chakvetadze, but was surprised when her opponent retired with a left thigh injury.

"I started well today," said Jankovic, who shared a birthday cake on court after the match with her Serbian fans.

"I was playing pretty aggressive tennis and didn't really give her a chance from the beginning. I didn't realise she had something wrong until the very end when she called the trainer."

Reuters