CARLSBAD, Calif. -- Kim Clijsters lost in the United States for the first time in nearly two years, dropping a 6-4, 6-4 decision to unseeded Shuai Peng of China in the quarterfinals of the Acura Classic on Friday night.
The 10th-ranked Clijsters, coming off an impressive win over Venus Williams in the final of the Bank of the West, had her streak of 26 straight hard-court victories in the United States snapped. It was her first loss in the U.S. since falling to fellow Belgian
Justine Henin-Hardenne in the 2003 U.S. Open final.
Peng advanced to the semifinals by beating her third straight seeded opponent.
"I didn't want to think too much," said Peng, who faced Clijsters for the first time. "If I get a chance, I just want to take the chance to win the point."
Peng, ranked 46th, will face sixth-seeded Mary Pierce in one semifinal on Saturday. Pierce defeated fifth-seeded Patty Schnyder 6-4, 6-3 and is the only seeded player to reach the semifinals.
"I felt like I was moving good out there and she just came up with better shots every time," said Clijsters, who was seeded seventh. "I was defending well and she kept going for it. All the credit to her.
"I think she has a great future ahead of her. She's been probably the best player I've played in a long time. I think she can definitely became a top three [player]," Clijsters added.
The other semifinal will include two Japanese players, Ai Sugiyama and Akiko Morigami. The winner will become the first unseeded player to reach the Acura final since Pierce lost to Lindsay Davenport in 1998.
Sugiyama advanced with a 6-1, 6-2 victory over 15-year-old Sesil Karatantcheva of Bulgaria. Morigami moved into the semifinals with a 6-3, 6-4 win over Anna Chakvetadze of Russia.
Peng also scored straight-set victories over third-seeded Elena Dementieva in the second round and 16th-seeded Dinara Safina in the third round.
With the players holding serve in the first set, Peng came through with a service break in the ninth game to take a 5-4 lead. After Clijsters saved two sets points, Peng won the set on her third set point when she ripped a backhand down the line.
Peng broke Clijsters in the first game of the second set and took a commanding 4-1 lead with another break. But Clijsters, a former world No. 1, cut the lead to 5-4 but sliced a backhand long to end the match.
Pierce had little trouble dispatching the fifth-seeded Schnyder, the highest remaining seed in the tournament. She used an early break to win the first set and then asserted herself in the second set, controlling many of the points in the quarterfinal match.
"I was fairly happy. I played well," Pierce said. "I knew I needed to be aggressive today. I played good enough to win."
Acura is the first Tier I tournament since the inception of the tier system in 1980 in which none of the top four seeds advanced to the quarterfinals. A number of top players withdrew from the tournament because of injury, including No. 1-ranked Davenport.
The 30-year-old Pierce, the oldest remaining player in the field, is having one of her best seasons in years. The two-time Grand Slam champion was the runner-up to Henin-Hardenne at the French Open. It was her first Grand Slam final appearance since
winning the French in 2000. Pierce also reached the quarterfinals at Wimbledon before losing to eventual champion Venus Williams.
Pierce, who raised her career record against Schnyder to 6-2, started the year ranked 29th but has raised her ranking to No. 14.
Pierce made a service break in the third game stand up against her Swiss opponent. After trading breaks early in the second set, Pierce broke Schnyder's serve again in the seventh game to take a 4-3 lead. Schnyder held off three match points before finally
hitting a backhand into the net.
"She puts huge pressure on me," Schnyder said. "She is so present on the court. She really forces you back. It's tough to get the rallies going and move her around."
Sugiyama gained the semifinals for the first time in 19 tournaments this season. Sugiyama, just a few months younger than Pierce, received an early break when Karatantcheva double-faulted in the third game. The unseeded Karatantcheva failed to hold her serve the rest of the set and scored just two points in Sugiyama's three service games.
"The score looks easy," said the 30-year-old Sugiyama, who upset No. 2 seed Svetlana Kuznetsova on Thursday. "For me, it was not easy at all, especially the first set where there were long rallies and I had to run to get the points."
Morigami, ranked 61st, reached her third semifinal of the season by eliminating the last of 11 Russian players in the event.
"Anna stayed pretty solid and I just tried to hit the ball in the court, which was very difficult," Morigami said. "I had to use a variety [of shots], like a slice or a topspin."