Kvitova defeated Lucie Safarova 6-3, 6-3 and thus clinched first place in the U.S. Open series.
By winning the points race leading up to the final major championship of the year, she gave herself a chance to collect $1 million in bonus prize money if she wins the U.S. Open. A runner-up finish in that tournament would earn her an additional $500,000.
Wozniacki, seeking her fifth straight championship in this event, ousted Dominika Cibulkova 6-2, 6-1.
Wozniacki will meet Maria Kirilenko in the semifinals after the seventh seed blasted Olga Govortsova 6-1, 6-2.
Sara Errani set up a semifinal meeting with Kvitova by defeating Marion Bartoli 6-4, 6-2.