ZURICH, Switzerland -- Top-ranked Kim Clijsters and No. 2 Justine Henin-Hardenne won in straight sets Friday to reach the semifinals at the Swisscom Challenge.

Clijsters beat Slovenian qualifier Tina Pisnik 6-3, 6-2, while Henin-Hardenne needed five match points before defeating seventh-seeded Vera Zvonareva 6-4, 6-2.

"It was a good match. I fought hard. I had to be very solid, much more solid than the score reflected,'' Henin-Hardenne said. "I haven't played this well since winning at the U.S. Open.''

The two Belgians are a victory each away from another meeting in a tournament final. Clijsters beat Henin-Hardenne in the title match at Filderstadt, Germany, last weekend to hold on to No. 1.

Henin-Hardenne next faces French Open semifinalist Nadia Petrova, who eliminated Elena Bovina 6-1, 6-4. Clijsters will play Jelena Dokic, who beat defending champion Patty Schnyder 6-0, 6-3.

Also Friday, Henin-Hardenne withdrew from next week's tournament in Linz, Austria, citing fatigue. She won the event last year.

"Unfortunately I have no option but to rest after this week to ensure that I will be 100 percent for the WTA Championships in three weeks' time,'' Henin-Hardenne said. "It's going to take everything I have just to survive and get through this week.''