Moscow - Top-seeded Svetlana Kuznetsova beat ninth-seeded Hungarian Timea Babos 7-5, 6-7 (2), 6-2 in the quarter-finals of the Kremlin Cup on Thursday to remain on course to claim the final spot in the WTA Finals.
Kuznetsova will qualify for next week's eight-player finals in Singapore only if she wins the Moscow tournament.
Otherwise, the place will go to Britain's Johanna Konta.
The Russian jumped to a 3-0 lead over Babos in the final set and converted on her first match point.
In the semifinals, Kuznetsova will meet fourth-seeded Elina Svitolina of Ukraine, who eased past Croatia's Ana Konjuh 6-1, 6-1.
In other quarter-final matches, Daria Gavrilova played seventh-seeded Anastasia Pavlyuchenkova, and Daria Kasatkina faced Julia Goerges later on Thursday.
ATP/WTA Kremlin Cup results in Moscow on Thursday (x denotes seeding):
Pablo Carreo-Busta (ESP x6) bt Damir Dzumhur (BIH) 6-3, 2-1 - retired
Daniil Medvedev (RUS) bt Viktor Troicki (SRB x4) 3-6, 6-3, 6-1
Thomaz Bellucci (BRA) bt Andrey Kuznetsov (RUS) 6-3, 3-6, 6-3
Philipp Kohlschreiber (GER x3) bt Dusan Lajovic (SRB) 7-5, 3-6, 6-3
Svetlana Kuznetsova (RUS x1) bt Timea Babos (HUN x9) 7-5, 6-7 (2/7), 6-2
Elina Svitolina (UKR x4) bt Ana Konjuh (CRO) 6-1, 6-1
Julia Goerges (GER) bt Darya Kasatkina (RUS x8) 7-5, 6-1