NEW YORK: Romanian teenager Simona Halep stunned French Open champion Li Na 6-2, 7-5 on Tuesday in the first round of the US Open tennis championships.

Halep, ranked 53rd in the world, needed just an hour and 33 minutes to dispatch China's sixth-ranked Li, who became the first Grand Slam champion from Asia with her victory at Roland Garros.

Since that triumph, Li has become a heroine in her homeland, but she has struggled on the court, losing in the second round at Wimbledon to eventual semifinalist Sabine Lisicki.

Her run to the semifinals at New Haven last week marked the only time she has put back-to-back match wins together since Roland Garros.

On Tuesday, Li looked out of sorts from the start, and Halep, 19, took full advantage to notch her first victory over a top-10 player in four attempts.

After taking the opening set, Halep gained an early break to lead 3-1 in the second.

Li squandered a golden opportunity when she failed to convert a triple break point in the sixth game.

Li finally managed to get the second set back on serve in the eighth game, then held to take a 5-4 lead.

In the end, however, she couldn't overcome 54 unforced errors -- the last a backhand long on match point.

Li's exit leaves the women's field without all three of this year's Grand Slam champions.

Australian Open champion Kim Clijsters, winner of the last two US Open titles, is absent with a stomach muscle injury. Wimbledon champion Petra Kvitova lost on Monday.