World number four Jessica Pegula and Russia's Veronika Kudermetova on Saturday advanced to the final of the Pan Pacific Open in Tokyo.
Pegula of the United States beat Greek star Maria Sakkari, ranked sixth in the world, 6-2, 6-3.
Pegula said she was "super happy" with the win, adding: "I'm proud of the way I competed today."
In Sunday's final, she will face the 19th-ranked Kudermetova, who beat the American in Madrid this year.
"I will try to learn from the last time I played her," said Pegula, who is aiming for her second title of the season following victory last month in Montreal.
Kudermetova had a tough semi-final, needing three hours and 25 minutes to defeat Anastasia Pavlyuchenkova 7-6 (8/6), 6-7 (2/7), 6-3.
But Pegula said this will give Kudermetova "a lot of confidence going into tomorrow".
Sakkari said she "felt a bit tired" in the semi-final.
"Last week's (tournament), travelling, the last matches, jetlag and everything didn't help today," she said.
"Jessica played really well on this court. It's low-bounce, it's fast. It's great for her."
Sakkari had ended her four-year wait for a second WTA title at the Guadalajara Open last week.
Kudermetova served 16 aces against Pavlyuchenkova, but said she "lost a little bit of concentration and started to play a little bit slow" in the second set.
It was important "to play aggressive", said the 26-year-old, who stunned four-time Grand Slam champion Iga Swiatek this week.
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