DUBAI, United Arab Emirates - Defending champion Caroline Wozniacki reached the semifinals of the Dubai Tennis Championships yesterday, while U.S. Open champion Sam Stosur was beaten by Jelena Jankovic of Serbia.

Wozniacki ousted Ana Ivanovic of Serbia 6-3, 7-5 in a meeting of former No. 1s, after Jankovic had beaten Stosur 6-4, 6-2. The 22-year-old Wozniacki eased through the first set and then overcame tougher resistance in the second before overcoming the Serb 1 hour, 33 minutes.

"I'm very pleased to get through that in straight sets," Wozniacki said. "Ana really stepped it up in the second set, took the balls very early, and just played really well actually. She took her chances and had nothing to lose."

Wozniacki is the highest-seeded player left in Dubai at No. 3 after top-ranked Victoria Azarenka pulled out of the tournament Wednesday because of an ankle injury. Azarenka unseated Wozniacki from the No. 1 ranking last month by winning the Australian Open. Now at No. 4, Wozniacki says she is determined to regain the top spot - and perhaps finally getting the first Grand Slam title of her career this year.

Wozniacki will play Julia Goerges today after the unseeded German defeated Daniela Hantuchova of Slovakia 4-6, 6-3, 6-4.

Earlier, the eighth-seeded Jankovic was in control throughout the match as the fourth-seeded Stosur struggled with her game. The Australian seemed to rush her shots for much of the first set, hitting the ball early and returning it long and wide. Stosur broke Jankovic early in the second, but the Serb broke right back and then pulled ahead 5-2 before wrapping up the match in 1 hour, 30 minutes.

The 26-year-old Serbian player also defeated Stosur in last year's quarterfinals in Dubai.

"I think the key was my return," Jankovic said. "It's never easy to return her serve. "But usually she likes to serve and then start dictating the point with her forehand. I didn't really allow her to do that ... I was pretty much in control the whole time," Jankovic said.

Jankovic will meet fifth-seeded Agnieszka Radwanska in the semifinals on Friday. The Polish player advanced after defeating ninth-seeded Sabine Lisicki of Germany, 6-2, 6-1.