Top-seeded Venus Williams will play for her 50th WTA title on Sunday in Stanford, in the tournament where she made her professional debut 22 years ago.
Williams defeated tenacious Alison Riske 6-1, 7-6 (7/2) to reach the championship match, where she'll face third-seeded Briton Johanna Konta.
Konta, ranked 18th in the world, reached her first career WTA final with a 6-4, 6-2 victory over second-seeded Slovakian Dominika Cibulkova.
After sailing through the opening set, Williams had to fight her own inconsistent serve in the second.
Up 5-4 in the second and serving for the match, Williams produced three double faults, wasting two match points.
Two games later Williams saved two set points to force the tiebreaker, which she dominated.
Williams, who won the Stanford title in 2000 and 2002, won her 49th career singles title in Taiwan in February.
The 36-year-old winner of seven Grand Slam titles turned back the clock with a run to the semi-finals at Wimbledon.
Konta, who reached the semi-finals of the Australian Open in January, and at Eastbourne in June, has rebounded well from a second-round exit at the All England Club.
"I'm really happy to have come through that and to be in my first final," Konta said. "I'm really happy that it's here in California, where the weather is unbelievable."
Konta dominated on serve, winning four of her five service games in the first set at love.
She closed out the first frame with an ace, and delivered more of the same in the second set, when she won 27 of the 29 points on which she put her first serve in play.
"I definitely felt I needed to take care of things on my end the best possible way," Konta said. "I was very effective with my breathing and just really playing within myself."
Cibulkova said power wasn't Konta's only advantage on serve.
"Her placing was very good," Cibulkova said. "Her serve was fast, but it wasn't the main problem. She was just placing the serve really well, and it was really hard to read it."
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