In Friday's semifinals, the second-seeded Kuznetsova, a former U.S. Open champion, rallied to beat fourth-seeded Serbian Jelena Jankovic 5-7 6-4 6-3.
"As the match was going longer and longer and I was starting to play better and better," Kuznetsova said. "I wasn't at my best, but it was important that I stayed focused because when I have played her in the past I have missed many chances and got frustrated. In the final set I was mixing it up well and all the time just making sure I stayed clam and I played my own game."
Dementieva, the eighth seed and two-time runner-up in major tournaments, staged a similar comeback to overcome Italy's Francesca Schiavone 5-7 7-5 6-2.
When the fellow Russians meet, they will be playing for $250,000.
Kuznetsova has a 5-3 lifetime edge.
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