NEW YORK -- Women's defending champion Serena Williams had no trouble advancing to the third round, beating Russian Nadejda Petrova 6-3, 6-2. Williams, with her sister Venus watching at courtside, served six aces and slugged 17 winners to just five for Petrova.

Still, Williams wasn't satisfied.

"Usually, I never lose serve," she said. "Already in this tournament I've lost serve twice. That's more than I've lost in the past two tournaments combined."

	Mary Pierce was 0-3 lifetime against Magdalena Maleeva until Thursday's second-round victory.

For Lindsay Davenport, once she got her game in gear, she raced into the third round of the U.S. Open tennis championships.

Davenport, seeking her second Grand Slam title of the year and seeded second here, was outplayed in the opening set before pounding out a 4-6, 6-2, 6-2 victory over 17-year-old Kim Clijsters of Belgium.

"I felt like I was hitting the ball and dictating the points in the second and third sets," Davenport said. "She was hitting the ball pretty well. She's a tough opponent and I'm happy to get through."

Earlier, there were a couple of surprises in the women's singles.

Lilia Osterloh of Canal Winchester, Ohio, upset 14th-seeded Dominique Van Roost 7-6 (9-7), 6-4, and Shinobu Asagoe of Japan ousted Patty Schnyder of Switzerland 7-5, 6-4.

Besides Davenport and Williams, other early second-round winners included fourth-seeded Mary Pierce, No. 7 Conchita Martinez, No. 12 Anna Kournikova, Elena Dementieva of Russia and Lisa Raymond.

Last year, Clijsters was four points away from defeating eventual champion Serena Williams in a third-round match. Against Davenport, she was the steadier of the two in the opening set, keeping Davenport on the run with hard-hit groundstrokes deep into the corners.

It was the game Davenport plays, and Clijsters was playing it better -- until the second set.