Ivanovic, the runner-up at the French Open and a Wimbledon semifinalist, had numerous errors against the hard-hitting Ukrainian. The 21-year-old Bondarenko advanced to her second quarterfinal of the year and will play Tatiana Golovin, last year's runner-up.

"I am not surprised, I prepared well for this tournament," said Bondarenko, who has yet to advance past the quarterfinals of a tournament.

Asked if this was the biggest win of her career, she said: "Yes, it is."

Henin, who also won the French Open this year, took a month off after the U.S. Open.

"I had a nice long rest, and it's a good win for me today," Henin said. "It's good to be back."

Defending champion Nadia Petrova eased into the quarterfinals with a 6-1, 6-3 victory over qualifier Michaella Krajicek.

Another Serb, third-seeded Jelena Jankovic, rallied to beat Shahar Peer 4-6, 6-1, 6-3.

"She doesn't give you any free points," said Jankovic, seeking her fifth title of the year. "You have to fight for every point."

In the quarterfinals, Jankovic will play Petrova, and Serena Williams, who advanced Wednesday, meets Svetlana Kuznetsova. Henin will play Elena Dementieva or Daniela Hantuchova.

The 19-year-old Ivanovic was coming off her third tournament victory this year in Luxembourg, where she also qualified for next month's season-ending WTA Championships in Madrid.

"I am definitely very disappointed, I came here with high expectations," Ivanovic said. "But she played an amazing match, she didn't do much wrong."

Ivanovic was in early trouble against the 46th-ranked Bondarenko. She dropped her serve in the opening game and struggled with her serve throughout the match.

The Serb pulled even at 2-2, following two straight double-faults by Bondarenko, but she didn't win another game in the first set.

Ivanovic called for her coach during the changeover and came out strong in the second, breaking Bondarenko's serve twice to go up 5-0 before winning the set.

"She played better in the second set, but I was also rushing," said Bondarenko, whose older sister Alona is also on the tour.

Another error by Ivanovic, a netted forehand, gave Bondarenko the decisive break and a 5-3 lead in the third. Ivanovic saved two match points in the next game, then sent another forehand long to end it.

Ivanovic said she was "emotionally drained" after beating Patty Schnyder 6-0, 6-2 Wednesday.