PARIS - Maria Sharapova saved her most piercing shriek to punctuate her final shot of the first set, a thunderous cross-court backhand winner to close out a tiebreaker.

She then dominated the rest of the way yesterday to beat Karin Knapp, 7-6 (4), 6-0, in the third round of the French Open.

The top-ranked Sharapova needed 81 minutes to win the opening set. She squandered a lead and fell behind in the tiebreaker, then benefited from some shaky shots by Knapp. But beginning with that ferocious backhand, Sharapova played her best tennis of the week.

"It was like my twin sister was here, and then Maria actually made her flight and made it for the second set," Sharapova said. "I definitely became a lot more aggressive and stepped in and didn't give her too many easy balls."

Top-ranked Roger Federer was aggressive from the start and defeated Mario Ancic, 6-3, 6-4, 6-2. Ancic is the last player to beat Federer at Wimbledon - in 2002 - but has lost their last five meetings.

"I was very pleased the way I played, because I always think on any surface, Mario's tough," Federer said. "Maybe a little tougher on a faster court, but nevertheless I'm happy with my performance."

Federer will next play unseeded Frenchman Julien Benneteau, who beat Robin Soderling, 1-6, 7-6 (6), 6-0, 6-1, then threw his shirt and shoes to the jubilant crowd.

The lone remaining American in either draw, Robby Ginepri, won again and became the first U.S. man to reach the fourth round at Roland Garros since Andre Agassi in 2003.

Ginepri extended his improbable run by beating Frenchman Florent Serra, 6-4, 6-4, 6-4.

"I would definitely like to have a lot of the other Americans still in the tournament," Ginepri said. "I'm really not trying to let that weigh on my shoulders."

No. 4 Nikolay Davydenko blew a big lead and lost to No. 28 Ivan Ljubicic, 4-6, 2-6, 6-3, 6-2, 6-4. No. 5 David Ferrer won a seesaw marathon against No. 25 Lleyton Hewitt, 6-2, 3-6, 3-6, 6-3, 6-4.

Ginepri, ranked 88th, came into the tournament 6-24 on clay and 0-5 at the French Open, but he has now reached the final 16 at all four Grand Slam events.

Ginepri will next play No. 24 Fernando Gonzalez, who outlasted No. 9 Stanislas Wawrinka, 5-7, 2-6, 6-4, 6-4, 6-4.

With no U.S. women left in the tournament, perhaps Americans can claim 18-year-old Belarussian Victoria Azarenka, who has lived and trained the last two years in Scottsdale, Ariz. The 16th-seeded Azarenka beat No. 18 Francesca Schiavone, 6-1, 6-1, and has lost only six games in her three matches.

Azarenka will next play No. 4-seeded Svetlana Kuznetsova, who faced only one break point and beat Nadia Petrova, 6-2, 6-1.

After winning the Australian Open in January, Sharapova needs only a French Open title to complete a career Grand Slam. Clay is her least-favorite surface, and she is the top seed only because four-time champion Justine Henin retired two weeks ago.

She will next play Dinara Safina, seeded 13th, who defeated Zheng Jie, 6-2, 7-5. Safina beat Sharapova in the fourth round of the French Open two years ago.