Belgian tennis star Kim Clijsters punctuated her return to the top of the women's world tennis rankings with a straight-sets win over American Chanda Rubin on Sunday.

Clijsters picked up her eighth tournament victory of the season at the SEAT Open tournament in Luxembourg, as she beat Rubin 6-2, 7-5. It was third her straight title, and ties her for total wins this season with fellow-Belgian Justine Henin-Hardenne, who she will replace at the top of the rankings on Monday.

Rubin is ranked 10th in the world and has lost all six of her matches against Clijsters. The American also fell eight points behind Japanese player Ai Sugiyama in the race to secure the eighth spot for next month's WTA Tour Championships. Whoever performs better in Philadelphia next week should qualify.

Second-seeded Ai Sugiyama of Japan defeated number-four Nadia Petrova of Russia in straight-sets to win the Generali Open tennis final in Linz, Austria.

Sugiyama beat Petrova 7-5, 6-4 on Sunday to claim her second WTA Tour title this season. The Japanese player was aggressive on the big points, while Petrova appeared to be nervous in her first career final.

Petrova jumped to a 2-0 start, but Sugiyama began to run down the Russian's shots and won four games in a row to lead 4-2. She then saved a break point and served out the opening set 7-5. In the second set, Sugiyama broke Petrova's serve in the first game and held serve the rest of the way for her fifth career title.

Tennis star Venus Williams has withdrawn from the Advanta Championships, due to start this week in Villanova, Pennsylvania, citing an abdominal strain that has been bothering her since last April.

Williams is ranked sixth in the world but hasn't played since aggravating a stomach muscle injury at Wimbledon. Her publicist said she still hasn't decided if she will play in nextg month's season ending WTA Championship in Los Angeles.

Venus' sister Serena, ranked number three in the world, withdrew from the Advanta championship last August after undergoing knee surgery that ended her season.