Elena Rybakina rallied from a set down to beat Coco Gauff 3-6, 6-4, 6-4 on Thursday and book a US Open championship showdown with two-time defending champion Aryna Sabalenka.
In Saturday's final Rybakina will try to deal another blow to Sabalenka, having knocked her out of the No 1 world ranking just by reaching the semifinals.
"I feel like I definitely need to step my game up, serve much better than today and stay aggressive," Rybakina said of her looming clash with Sabalenka.
Gauff's bid to return to the final for the first time since she defeated Sabalenka for the 2023 title had got off to a smooth start, with the American seizing the initiative in the opening set with a break to go 4-2 up.
She held to love to take a 5-2 lead and then held in the ninth game to take a one set lead.
But Rybakina hit back with an early break of serve in the second set for a 3-1 lead and held to go 4-1 up.
Gauff responded superbly to claw her way back into contention with a break to make it 4-3 before holding to square it a 4-4.
Yet she was unable to make the most of her fightback and double-faulted in the 10th game to hand two set points to Rybakina at 15-40. Rybakina pounced on that chance to take the match to a third set.
The decisive set followed a similar pattern.
Gauff conceded a break to trail 5-3 and leave Rybakina serving for the match.
But the American broke back immediately to make it 5-4 to get it back on serve.
Again though Gauff was unable to capitalise, and a deft volley from Rybakina left her with two match points at 15-40, before Gauff then hit a wide open smash long to hand her opponent victory.
"It was such a cool third set – I feel like I was a little bit lucky on her serve," Rybakina said. "A couple of deep returns, one mistake from her, it went quickly my way...it was a real battle."