MELBOURNE, Australia -- Defending champion Serena Williams and top-ranked Justine Henin pushed aside two more overmatched opponents in the Australian Open, advancing to the fourth round with straight-set victories today.

Williams, 26-1 with three titles at Melbourne Park since the start of 2003, beat No. 26 Victoria Azarenka 6-3, 6-4.

Henin, 15-1 in Melbourne since the start of the 2004 tournament that she won, overcame serving troubles to hold off 25th-seeded Francesca Schiavone 7-5, 6-4.

Henin extended her winning streak to 31, dating to the Wimbledon semifinals. But the Belgian star's path to the championship is tough, with both of last year's finalists potentially in her path.

Williams, who was unseeded and ranked No. 1 when she beat then top-seeded Maria Sharapova here last year to claim her eighth Grand Slam title, fired 15 aces and had a stretch of seven service games in which she yielded only six points.

Williams also was painting the lines with her groundstrokes, contributing to 29 winners. When she made her 25 unforced errors, it usually was by a matter of inches.

"I feel pretty good about where I am," she said. "Hopefully, I'll peak later in the tournament."

Williams will face No. 12 Nicole Vaidisova, a 6-3, 6-4 winner over Japan's Ai Sugiyama 6-3, 6-4. Williams had to save set points in a semifinal against Vaidisova here last year before winning in straight sets.

"Obviously, it doesn't get much tougher than that," Vaidisova said of the fourth-round match against Williams. "She's a great champion, a great fighter.

"I'll definitely have to have my A game on."

No. 5 Sharapova faced fellow Russian Elena Vesnina later in the day.

No. 3 Jelena Jankovic, who had to save match points in her first-round match, had a lapse in the second set and a code violation for coaching in the second game of the third set of a 6-2, 4-6, 6-1 win over No. 30 Virginie Razzano of France.

Henin will play Taiwan's Hsieh Su-wei, who beat Aravane Rezai 6-2, 6-7 (3), 6-4 in the third round.

"I hate to look too far," Henin said. "I just want to get ready, improve my game and be in my best shape. I know the draw, but I like to stay concentrated on myself."

After retiring from the 2006 Australian final against Amelie Mauresmo because of a stomach illness, Henin skipped the event last year because she was going through a divorce.

She has dominated the women's tour since returning, finishing 63-4, including two majors and the season-ending championship, in 2007. She added the Sydney International title last week to build up for Melbourne Park.

She got only 48 percent of her first serves and had her serve broken three times, and was lucky it didn't cost her more against Schiavone.

"It was really exciting. I'm glad to win in two," Henin said. "She's always given me trouble in the past, so it was a tough third round for me."

Men's No. 4 Nikolay Davydenko has not dropped a set in three rounds, beating France's Marc Gicquel 6-3, 6-2, 6-3 on Friday.

Jo-Wilfried Tsonga had a straight sets win over Guillermo Garcia-Lopez of Spain.

Marcos Baghdatis downed 2005 champion Marat Safin 6-4, 6-4, 2-6, 3-6, 6-2 in a momentum-swinging match that started Thursday and stretched into Friday morning and completed the second round.

Safin was the last player to beat top-ranked Roger Federer in Melbourne, breaking up the Swiss star's four Australian titles with a semifinal upset three years ago.

Baghdatis is one of three losing Australian Open finalists still in contention -- a list that will certainly be reduced in the third round. He will play 2005 runner-up Lleyton Hewitt next. Fernando Gonzalez, who lost last year's championship match, is still in the equation.

Video of Baghdatis, a Greek Cypriot, holding a flare and reportedly yelling "Turks Out," emerged in the Australian media on Friday, 10 months after it was posted on a video sharing Web site.

The 2006 runner-up did not apologize for the video in a statement released Friday in response to criticism from Melbourne's Turkish-Cypriot community, saying he wanted to concentrate only on the tennis.

Cyprus has been divided along ethnic lines since 1974.

The International Tennis Federation and Tennis Australia both said they would not be making any comment.

Federer, aiming for a third straight Australian title, won the last 10 games in a 6-1, 6-2, 6-0 win over Fabrice Santoro on Thursday, ending the 35-year-old Frenchman's record 62nd major in the second round.

He has reached the finals of the last 10 Grand Slam tournaments and won eight of them, losing twice to Rafael Nadal at the French Open.

Nadal and Roddick are into the third round and playing later Friday. Nadal faces No. 28 Simon Gilles and sixth-seeded Roddick is against Philipp Kohlschreiber in a night match.