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 (4), 7-6 (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 21/2-year hiatus. But now 29 and a mother, she 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.”

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.

She missed the hard-court major in 2004, 2006-08 and last year, thanks to a combination of injuries and the time she took off while starting a family. Her daughter, Jada, was born in February 2008. By August 2009, Clijsters was back on tour; unseeded and unranked, because she only played in two previous tournaments during her comeback; she won that year’s U.S. Open.

“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.”

Her previous defeat at Flushing Meadows came against Belgian rival Justine Henin on Sept. 6, 2003, in the tournament final. Robson was 9 at the time.

This did have the feel, in some ways, of a changing of the guard.

Clijsters finished with a career singles record of 523-127 (a winning percentage of .805) and 41 titles, including her last major trophy at the 2011 Australian Open. She spent a total of 20 weeks ranked No. 1, as recently as February 2011.

Ranked 89th and with only one prior victory over a top-25 player, Robson has been viewed — particularly back home in Britain — as an up-and-coming player whose smooth left-handed strokes would carry her far.

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 American wild-card entry Mallory Burdette, the NCAA runner-up who reached the third round in her Grand Slam debut by eliminating 69th-ranked Lucie Hradecka, 6-2, 6-4.

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

Burdette next faces four-time major champion Maria Sharapova, a 6-0, 6-1 winner Wednesday night over 78th-ranked Lourdes Dominguez Lino of Spain.

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

“I know in the nitty-gritty times of a match, I always have that confidence and all those wins in my back pocket,” said Isner, who is 37-13 in tiebreakers this season.

The 6-foot-9 Isner hit 20 aces and ended things with a service winner on his third match point. That came after Malisse pushed an easy backhand volley into the net, then grabbed the ball and shoved it in his mouth and chomped on it as though it were an apple.

In a night match, No. 3 Andy Murray — the Olympic gold medalist — reached the third round for the seventh straightyear, beating Ivan Dodig, 6-2, 6-1, 6-3.