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

She then dominated the rest of the way Saturday 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.

In the second set, 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."

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. Ranked 88th, Ginepri 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 was steadier than Serra, losing serve just once and committing only 18 unforced errors to 43 for the Frenchman.

"He is the one who forced me to make errors," Serra said.

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 past two years in Scottsdale, Ariz. The No. 16-seeded Azarenka beat No. 18 Francesca Schiavone 6-1, 6-1 and has lost only six games in three matches this week.

Azarenka took advantage of Schiavone's weak second serve, winning 23 of those 28 points. Since the start of the year, Azarenka has climbed in the rankings from 30th to a career-high 17th.

"This year I improved a lot my forehand, which was my weak shot," she said. "Now it's like my weapon, which helps me a lot."

Azarenka will next play No. 4-seeded Svetlana Kuznetsova, who faced only one break point and beat Nadia Petrova 6-2, 6-1. Kuznetsova, the 2004 U.S. Open champion, beat Azarenka in their two previous meetings, both on hardcourt.

"She's a big player, but she's also human," Azarenka said. "I played her two times already. It probably won't be that scary anymore."

Against Petrova, Kuznetsova hit five aces and lost only five points on her first serve. She said she changed her service motion two months ago.

"I need my serve more than ever, so I'm really focused on it, and I feel like I'm doing much better," Kuznetsova said. "I feel so much power in it, more consistent. I feel really good when I can get everything together."

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's top-seeded only because four-time champion Justine Henin retired two weeks ago.

In a sign that it won't be easy, Sharapova needed 6½ hours to win her first three matches.

"We're playing on a surface that's going to make you hit more balls and that's going to be more physically challenging," she said. "But, you know, I'm mentally prepared for that."

To keep winning, she'll need to improve her serve. Sharapova had nine double-faults against Knapp, giving her 36 in three matches.

"Sometimes it becomes a steamroll," Sharapova said. "It's fine. I have double-faulted numerous amounts of times in my career. Today was an improvement. It is a lot better — felt more comfortable."

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

In the completion of a match suspended due to darkness, No. 3 Jelena Jankovic defeated No. 28 Dominika Cibulkova 7-5, 6-3. Jankovic led 4-2 in the second set when play was halted Friday.

On the men's side, No. 5 David Ferrer won a seesaw marathon against No. 25 Lleyton Hewitt, 6-2, 3-6, 3-6, 6-3, 6-4.