Serena Williams, Dementieva through to Sydney final

Serena Williams survived a scare from France's Aravane Rezai on Thursday before booking her spot in the final of the Sydney International against Russia's Elena Dementieva.

Williams was teetering on the brink of defeat after losing the first set and trailing 5-2 in the second when she suddenly raised her game to win 3-6 7-5 6-4.

"I was lucky to get through today," Williams said. "I'm just super mentally tough, I feel like that's definitely one of my strengths."

While Williams had to dig deep, Dementieva had no real problems winning her semi-final against Victoria Azarenka of Belarus.

Dementieva cruised to a 6-3 6-1 victory at the Olympic tennis centre to remain on track to defend the title she won last year.

Williams was well below her best against Rezai but was able to use all her big match experience to turn things around in an ominous sign of her intentions ahead of next week's Australian Open.

"I felt like I literally lifted my game at that point, because I knew I was gonna be headed to Melbourne if I didn't," the world number one said.

"I kept thinking, I want to get a little more practice, and I'd hate for it to end now."

Rezai, who won two tournaments in 2009, was playing Williams for the first time and admitted the thought of beating the American contributed to her defeat.

"I was probably scared to win the match. But, you know, I realise I have the game and I can win, so I learn one more thing today.

"I think she's a fighter and is mentally  very strong. I wasn''t impressed, but I knew that she will fight. That's her game, that's how she plays."

While there was disappointment for Rezai, France were at least assured of a place in the men's final after Richard Gasquet and Julien Benneteu both won their quarter-finals.

Gasquet, who resumed playing this month after being cleared over a positive cocaine test, defeated Italy's Potito Starace 6-3 7-6 while Benneteau beat Leonardo Mayer of Argentina 6-4 6-7 6-0.

"I had so many things very hard to do last year, so now I play for fun," Gasquet said.

"I try my best to win, and that's the most important for me."

The pair will play each other in Friday's semi-finals while Lleyton Hewitt meets Marcos Baghdatis and Mardy Fish faces Peter Luczak in the remaining quarter-finals.