Third seed Clijsters had to draw on all her big-match experience and reserves of energy in the scorching heat to record a 6-1 1-6 7-5 victory, joining Jankovic in Friday's final at Sydney's Olympic tennis centre.
Jankovic produced an inspired performance in beating Nicole Vaidisova of the Czech Republic 6-4 4-6 6-4 to reach her second final in a week, despite struggling with lower back pain for most of her match against the eighth seed.
"I don't like to give up. It doesn't matter which tournament we are at," Jankovic said.
"I try always to give my best and to fight until the end and today I had a problem with my back but the trainer came out and she really helped me a lot.
"She loosened me up and I was able to finish the match and actually win, which I didn't believe at some moments."
Jankovic won last week's Auckland Classic then beat Martina Hingis, Samantha Stosur and Amelie Mauresmo in Sydney, but her golden run looked to be coming to an end against Vaidisova when she started to show signs of distress in the first set.
The 21-year-old twice called for help during the second set before taking a medical timeout, but she fought through the pain to chalk up a ninth straight victory this year.
"I was really struggling, especially with the heat and everything, but it's my ninth match today and I didn't have any rest," Jankovic told a news conference.
"It was really difficult for me but I was just telling myself I have to hang in there and fight until the end and that's what I did."
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
Li ran the Belgian ragged in the second set with her booming forehand before Clijsters regained her composure after a 10-minute heat break to wear down her opponent in the decider.
"She's the best Chinese girl out there," Clijsters told a news conference.
"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."
Clijsters sailed through her first two matches for the loss of just six games but said Li had given her the perfect workout she needed for next week's Australian Open.
"It's nice to be out on the court like this and be challenged," she said.
"Not just by your opponent but by the heat and everything, that makes it a lot more challenging."
Clijsters said she would have to raise her game even higher against Jankovic, who was one of the most improved players on the tour.
"I've played her a few times and I feel like every match that I've played against her she's become better," Clijsters said.
"She looks more confident out there. She could get really uptight and really angry at herself and lose a few games by just getting down on herself... but she's a lot more positive out there now."
Jankovic said she had no longer held any fears about facing the top players but was wondering how her body would hold up in the final.
"I will go to the physio room and I will have so many treatments, with my feet, with my back, with my groin," she said.
"I have so many things that are really hurting me at the moment, and I will have a massage, so I hope that I can recover for tomorrow's match."