Coco Gauff lost in straight sets - 6-3 6-3 - to fellow American Madison Keys in the semi-finals of the Eastbourne International.
Keys will face Russia's Daria Kasatkina, who beat Camila Giorgi 6-2 7-5, in the final on Saturday.
The win was Keys' first over a top-10 player on grass since she beat Angelique Kerber to win the 2014 tournament at Eastbourne.
Gauff, 19, faces world number 126 Sofia Kenin in the first round at Wimbledon.
Keys gained the upper hand in the fifth game of the match when she broke Gauff's serve - and then did so again to clinch the first set.
Gauff claimed an early break in the second set but her service game let her down as three consecutive double faults at 2-1 allowed Keys back in.
Keys, who has not dropped a set in the tournament, squandered three match points at 5-3, but held her nerve at deuce to serve out the match.
The 28-year-old had a painful fall in the fifth game of the second set at a blustery Devonshire Park and had to dig deep to progress.
"I just took a slip and my hip went in the direction it shouldn't have gone in. Hopefully it's fine for tomorrow," Keys said.
"It's definitely 10 times more difficult when you have to play Coco and then you throw in hurricane winds on top of it. So being able to make a final here where I won my first title is amazing."
Kasatkina sees off battling Giorgi
Kasatkina saw off a spirited fightback from unseeded Giorgi to secure her spot in the final.
The Russian comfortably took the first set and had been 4-1 up in the second, only for Giorgi to rally to pull it back to 5-5.
However, the Italian then failed to hold her next service game as Kasatkina went back through the gears to close out the match.
Kasatkina has been seeded 11th for Wimbledon and will play American Caroline Dolehide in the first round.
Russians and Belarusians will be back at the tournament after the All England Club lifted the ban it imposed last year because of the war in Ukraine.
Kasatkina has previously criticised her country's invasion of Ukraine and described the war as a "full-blown nightmare".
In the women's wheelchair singles semi-finals, British number one Lucy Shuker lost to defending champion and top seed Diede de Groot in straight sets.
De Groot triumphed 6-1 6-2 and will face fellow Dutch compatriot and second seed Jiske Griffioen in the final.