Rybakina prevailed in a fairly straight-forward first set in a match delayed by more than an hour - and then interrupted - due to persistent rain.

Ostapenko gained momentum in the second set and took a 3-0 lead but Rybakina shortened the distance to 4-2 just before rain briefly forced the players off court.

Rybakina was leading 40-15 in the game when play got suspended once more but the Kazakh player came out on top after it resumed, and rallied to win five games in a row in total to seal the victory.

"It was a really tough day overall, with all the rain delays. I'm just happy to be in the final," Rybakina told a news conference.

"I didn't start that well the second set. A bit low on energy, lost my serve. So it was difficult. Then a few good shots from (Ostapenko), good serves. It changed very quickly.

"I'm happy that physically I can maintain and stay so long in the tournament till the end."

In her third WTA 1000 final of the season Rybakina will face 30th seed Kalinina, after the Ukrainian survived a second-set scare against Veronika Kudermetova (26) of Russia in a battling 7-5 5-7 6-2 victory.

Kudermetova started strongly, but the tables quickly turned as the Russian failed to convert eight of her nine break-points in the first set, with her opponent capitalising on her wastefulness to edge ahead in the encounter.

Kalinina broke early in the second set to take a 3-2 lead and appeared on course for a comfortable win, but with her back against the wall Kudermetova mounted a spirited comeback, winning 16 straight points to level the match.

Kalinina headed off for a lengthy bathroom break to regroup before the third set and emerged a player reborn, playing with renewed confidence to win the first four games of the decider en route to sealing a spot in her first WTA 1000 final.