Serena Williams closed out the match with an ace.

THE ASSOCIATED PRESS

MELBOURNE, Australia -- Defending champion Serena Williams has advanced to her fifth Australian Open final and will put her 100 per cent record here on the line against Justine Henin, who is only two tournaments into her comeback from retirement.

Both advanced over Chinese players on Thursday to set up a championship match involving two former Australian champions.

Top-ranked Williams wasted four match points before finishing off a 7-6 (4), 7-6 (1) semifinal win with an ace against Li Na on Thursday, a day after her sister Venus lost to the Chinese player in the quarter-finals.

Henin overwhelmed 2008 Wimbledon semifinalist Zheng Jie 6-1, 6-0 in 51 minutes, the shortest match of this tournament and the most lopsided semifinal at the Australian Open since Chris Evert beat Andrea Jaeger by the same score in 1982.

Williams leads Henin 7-6 in career head-to-heads, although they've never met in a Grand Slam final. Williams won their last match, at Miami in 2008, just before Henin retired suddenly while holding the No. 1 ranking.

"I can't wait for the final. It's such an amazing chance that I have to play another final in Melbourne," said Henin, who won the 2004 title in Melbourne and retired with stomach problems during the 2006 final against Amelie Mauresmo. "It's a very special occasion, but the dream continues.

"I'm going to play the No. 1 player in the world in a Grand Slam final. She's a real fighter."

In men's doubles action Thursday, Toronto's Daniel Nestor and Serbian partner Nenad Zimonjic reached the final with a 6-4, 6-4 win over Croatia's Ivo Karlovic and Serbia's Dusan Vemic.

"It would really mean a lot to win a third Grand Slam," Nestor said. "We'd really like to branch out after winning Wimbledon twice. We've not done too well here so we hope to be able to get over that hump."

Serena Williams has won the women's title every time she's played for the championship since beating Venus here in 2003. The winning sequence has been every odd-numbered year so far.

"I really should have won sooner ... I had so many match points and I blew it and I knew I couldn't mess up my serve because she never gives up," Williams said after posting her 50th career win at Melbourne Park. "She's a real, real amazing fighter.

"Every time I had match points she came up with some big serves and great shots. She just goes for broke."

Williams, the 11-time Grand Slam singles champion, was joining Venus in a doubles semifinal in the afternoon.

China had two players into the semifinals of the same major for the first time but still is yet to get a finalist.

Henin has won seven Grand Slam singles titles but is into her first major since the 2008 Australian Open, when she lost in the quarter-finals to eventual champion Maria Sharapova.

Henin is unranked and two tournaments into a comeback from 20 months off the tour, hoping to emulate fellow Belgian Kim Clijsters' win at the U.S. Open.

Clijsters was only three tournaments into a comeback from two years off, and playing on a wild card entry, when she beat both Williams sisters en route to winning the title at New York.

Williams is hoping for better against a Belgian on the comeback this time. Her semifinal loss to Clijsters in New York cost her a record US$82,500 fine for a profanity laced tirade against a line judge who called her for a foot fault.

Against Li, she got on top by breaking in the opening game.

Li fended off a set point in the ninth game before holding, then broke Williams' serve in the 10th game to even the match at 5-5.

In the tiebreaker, Williams picked up four of her last five points on unforced errors by Li and then clinched the 58-minute set with a second-service ace.

The second set went with serve, with Li fending off three match points in the 10th game and another in the 12th to force a second tiebreaker. Again, Williams dominated the tiebreaker to race to a 6-1 lead, closing with her 12th ace of the match.

Venus Williams, who had a chance to serve for the quarter-final on Wednesday against Li before she lost, was watching from the stands. Chinese fans waving their red national flags were sitting in the rows behind her.

No. 5 Andy Murray and No. 14 Marin Cilic were to meet in a semifinal Thursday night after ousting the second- and fourth-seeded players in the quarter-finals.

With Jo-Wilfried Tsonga taking out No. 3 Novak Djokovic late Wednesday night, there was nobody left in the draw who has beaten Roger Federer in a major.

Murray was leading defending champion Rafael Nadal by two sets and a break when the Spaniard retired due to a knee injury; Cilic beat U.S. Open champion Juan Martin del Potro in five sets.

Tsonga beat 2008 champion Djokovic 7-6 (8), 6-7 (5), 1-6, 6-3, 6-1, in a reverse of the outcome of their final here two years ago, and will meet top-ranked Federer in a semifinal on Friday.

Federer advanced to his 23rd consecutive Grand Slam semifinal on Wednesday with a 2-6, 6-3, 6-0, 7-5 win over No. 6 Nikolay Davydenko.

Davydenko's 13-match winning streak was the hottest on tour and included two wins over Federer.

The Russian unloaded everything he had on Federer for a set and a half, until Federer's big-match experience kicked in, he switched gears and won 13 straight games to take the match away from Davydenko.

Federer has made the semifinals or better at every major since Wimbledon in 2004, a record he considers "definitely one of the most incredible things I have in my resume."