The 2011 Wimbledon champion Kvitova rallied to defeat former world number one Caroline Wozniacki 3-6 6-2 6-3 after Li had recovered from a 5-1 deficit in the deciding set to record a 3-6 6-3 7-5 victory over Lucie Safarova in the first semi-final.
While Kvitova has been consistent at grand slam level this season, the powerful Czech has yet to produce the form that claimed the Wimbledon crown and the WTA Championships in a breakthrough 2011 campaign.
However, her play in Montreal has been impressive since struggling to overcome Ksenia Pervak in her opening match of the $2 million tournament.
She next routed Marion Bartoli and Tamira Paszek and despite looking erratic early against Wozniacki, Kvitova was dominant once she found her groove and is looking forward to Monday's clash against the Chinese 2011 French Open winner.
"We (have) played each other, I think, three times already and I'm losing. So I have to win tomorrow to even it up at 2-2 and gain revenge," she said.
"I know that she's playing great tennis here and she's trying to play aggressively."
Wozniacki, who is also without a title since her success in New Haven last August, was unable to draw inspiration from the US PGA Championship success of her boyfriend Rory McIlroy.
The Dane watched McIlroy claim an eight-shot victory at Kiawah Island on television during a brief rain delay with the scores level at a set apiece but was unable to lift her game to a similar level following the break.
"It's great that Rory won. It's an unbelievable performance by him," she said. "I just tried to just relax a little bit and come out strong, but, you know, Petra just came out stronger than me."
Li's victory looked highly improbable when Safarova, who will be ranked in the top 20 for the first time at the completion of this event, was serving for the match at 5-1.
The sudden swing in momentum was as much down to Safarova faltering as Li's ability to eradicate errors from her own game.
Li's strategy was simple. She told reporters she just tried to keep the ball in the play when she sensed nerves could become a factor.
"This is tennis. You have to put ball back to the court and over the net," the 30-year-old said.
Safarova, who had troubled Li with her swinging left-handed serve for much of the match, admitted that nerves had indeed got the better of her.
"She used that situation to turn it over, and then she was serving very well, just started to play much better after that moment and it just slipped away," Safarova said.
Li, who thrashed world number three Agnieszka Radwanksa 6-2 6-1 in the quarter-finals, has lost finals in Sydney and Rome this season but is certain to climb back into the top 10 regardless of Monday's outcome.
- Caroline Wozniacki
- Lucie Safarova