Clijsters was pushed all the way by Li Na in Sydney

Clijsters, who won the Sydney title in 2003, looked to be cruising to an easy victory when she raced through the opening set in 28 minutes.

Li ran the Belgian ragged in the second set with her booming forehand before Clijsters regained her composure.

Jankovic reached the final after beating Nicole Vaidisova 6-4 4-6 6-4.

The Serb, who won last week's Auckland Classic before beating Martina Hingis and Amelie Mauresmo this week, looked in trouble when she twice called for medical help in the second set.

But the 21-year-old fought through the pain to chalk up a ninth straight victory this year.

Clijsters, the third seed, paid tribute to her opponent and admits she will have to improve if she is to beat Jankovic in Friday's final.

"Li Na is the best Chinese girl out there," she said.

"She's a very powerful girl and moves well, has a good serve, and she's a good player. She's really improved a lot.

"I've played Jelena a few times and every match that I've played against her she's become better.

"She looks more confident out there. She could get really uptight and really angry at herself but she's a lot more positive out there now."