Bondarenko proved too tough for Keothavong in Warsaw
Anne Keothavong's fine run at the Warsaw Open came to an end with a straight-sets defeat at the hands of Alona Bondarenko in the semi-finals.
British number one Keothavong struggled in the first set but made her opponent work harder for the second, before Bondarenko ran out a 6-2 7-5 winner.
Keothavong was the first British woman to reach the last four of a WTA clay-court event since 1983.
Bondarenko plays Romanian qualifier Alexandra Dulgheru in the final.
The 19-year-old Dulgheru, who is ranked 201st in the world, upset sixth seed Daniela Hantuchova of Slovakia 6-4 6-7 (2-7) 6-1.
Number eight seed Bondarenko, who beat former world number one Maria Sharapova earlier in the tournament, will be looking to go one better than in 2007 when she finished runner-up in Warsaw.
Keothavong was disappointed with the manner of her exit, but was pleased at making it to the latter stages of the event.
"It wasn't one of my best matches but Alona's a tough opponent," she said. "She makes you play every ball and she moves pretty well and I ended up forcing a little bit too much at times.
"I was getting better as the match wore on but it wasn't enough.
"I still thought I was in it in that second set and I had opportunities, so it's a shame I couldn't get it to go my way.
"Overall it's been a great week for me. I'm really pleased that I've made another semi-final, my third one this year and especially at a premier level and on clay.
"I can't be all disappointed. I have another match in Paris in a couple of days to think about."
Keothavong faces top seed Dinara Safina of Russia in the French Open next week.