SYDNEY  - China's Li Na fought back from a set and a break down to delay Petra Kvitova's bid for the world number one ranking in a tenacious semi-final victory at the Sydney International on Thursday.

French Open champion Li recovered to down Wimbledon winner Kvitova 1-6, 7-5, 6-2 in two hours of high-class tennis to reach her second consecutive Sydney final where she will face third seed Victoria Azarenka of Belarus.

In doing so, world number five Li frustrated the Czech left-hander's immediate hopes of toppling Caroline Wozniacki from the top of the women's rankings ahead of next week's Australian Open in Melbourne. Kvitova, trailing Wozniacki by just 295 rankings points, would have claimed the number one ranking if she had won the Sydney tournament, with 470 points up for grabs to the winner.

In the other semi-final, Azarenka fought back from a set down to beat Wozniacki's victor from the quarters, Polish seventh seed Agnieszka Radwanska 1-6, 6-3, 6-2 in almost two hours. "The way she (Kvitova) was playing in the first set I didn't know what to do. Give up? I couldn't do anything," Li said.

Defeat for the Chinese star looked certain after Kvitova stormed through the opening set losing just one game and broke early in the second set to lead 3-1, but Li took a grip on the match with fearless serving and shot-making.

"I think in the second set the match turned around because her service game was not like the first set where she was hitting winners all the time.” Several times Li saved break points with a brave deep second serve to stay in the match.

But as Li continued to frustrate Kvitova's attempts to finish off the match she gradually clawed back to finish the stronger. Li now leads Kvitova 2-1 in their matches. "After first set I called my coach to the court and he told me that if I continued to play like I was I would lose the match easy," Li said. "Like maybe after 50 minutes we can go to the airport. He said I had to believe in myself and do better. So I just tried to play more deeper and try to play more of my best tennis."

Kvitova recognised that she was not clinical enough, and after dominating the opening set she gave Li chances to get back into the contest. "I played very well the first set. I was the one who made the winners... And then in the second set, I gave her a lot of chances and she did it. It's tennis, so it's still up and down," said the world number two.”