NEW YORK — Kim Clijsters' singles career ended where she wanted it to, just not the way she hoped.

The four-time Grand Slam champion lost 7-6 (6-4), 7-6 (7-5) to 18-year-old Laura Robson of Britain in the second round of the U.S. Open on Wednesday, and will head into retirement after she finishes playing in doubles at Flushing Meadows.

Clijsters walked away from the sport once before, in May 2007, then returned after a 2 ½-year hiatus. But now 29 and a mother, the Belgian insisted this season that she means it this time, and decided the U.S. Open — and its hard courts that she conquered on the way to three championships — would be her final tournament.

"It's the place that has inspired me so much to do well and to do great things. It's hard to explain sometimes why," Clijsters said in an on-court interview, her face flushed and her eyes welling with tears.

"This completely feels like the perfect place to retire," Clijsters told the spectators at Arthur Ashe Stadium, many of whom rose to shower her with a standing ovation. "I just wish it wasn't today."

Third-seeded Maria Sharapova needed 54 minutes to advance to the third round.

The four-time Grand Slam champion beat Lourdes Dominguez Lino 6-0, 6-1 on Wednesday. Sharapova had 30 winners; the 78th-ranked Spaniard had zero. She next faces American wild-card Mallory Burdette, a 21-year-old Stanford All-American making her Grand Slam debut.

The loss Wednesday ended Clijsters' 22-match winning streak in New York, encompassing titles in 2005, 2009 and 2010, plus Monday's first-round victory.

"Since I retired the first time, it's been a great adventure for my team and my family," said Clijsters, who was 28-0 against players ranked outside the top 10 at the U.S. Open before Wednesday. "It's all been worth it. But I do look forward to the next part of my life coming up."

When the contest ended with Clijsters sailing a backhand return long, allowing Robson to convert her third match point, they met at the net. Clijsters began to extend her arm for the customary handshake, and Robson pulled her in for a hug.

"I want to thank Kim," Robson told the crowd moments later, "for being such a great role model to me for so many years."

Less than an hour later, Clijsters was hanging out in the players' garden alongside the stadium. She shared a laugh with some friends, hugs from others, and paused to pose for a photograph alongside 14-time major champion Serena Williams, who was headed out after partnering sister Venus for a first-round victory in doubles.

Clijsters was the only seeded woman who lost during the afternoon session of Day 3, when the winners included No. 1 Victoria Azarenka, defending champion Sam Stosur, 2011 Wimbledon champion Petra Kvitova and 2011 French Open champion Li Na.

Joining Robson with a surprise victory was Burdette, who reached the third round by eliminating 69th-ranked Lucie Hradecka 6-2, 6-4.

Until recently, Burdette planned to take pre-med courses as a senior at Stanford in pursuit of a career in psychiatry.

"It's been a crazy ride," the 252nd-ranked Burdette said.

Earlier on Ashe, the highest-ranked American man, John Isner, let out a big exhale of relief while waving to the crowd after getting past an argumentative Xavier Malisse 6-3, 7-6 (7-5), 5-7, 7-6 (11-9) in the first round.