French Open champion Mirra Andreeva beat American Jessica Pegula 6-3, 6-4 on Saturday to reach the WTA Finals championship match in Indian Wells, California.
With the semi-final win the 19-year-old Russian -- who won her maiden major at Roland Garros this year -- is assured of rising from third to second in the world rankings.
On Sunday she will face either Wimbledon champion Linda Noskova or Ukraine's Elina Svitolina for the title in the elite season-ending event, which was moved from Saudi Arabia to California in July because of war in the Middle East.
Andreeva remained unbeaten in her WTA Finals singles debut, having posted round robin victories over sixth-ranked Svitolina, world number two Aryna Sabalenka and Diana Shnaider.
For Pegula it was a match of missed chances, the fifth-ranked American unable to build on early breaks in both sets.
Andreeva double-faulted on break point to give Pegula a 2-1 lead in the opening set.
But the Russian broke back immediately, whipping a crosscourt forehand winner on her third break chance to make it 2-2.
Andreeva saved a pair of break points in the fifth game and broke again for a 5-3 lead.
Pegula had a chance to extend the set in the next game, but on break point she smashed what looked to be an easy backhand at the net past the baseline and Andreeva held to pocket the first.
Andreeva double-faulted to give Pegula a break chance in the fourth game of the second and the American converted for an imposing 3-1 lead.
But once again Andreeva broke back immediately, and broke again for a 4-3 lead.
She closed out the win after one hour and 25 minutes, giving herself a match point with an overhead winner before Pegula sent a backhand long.