Laura Robson dissolved into giggles at a reference to British boy band One Direction.

Yes, she's definitely 18. She also just defeated two former Grand Slam champions at the US Open, which is good because she'll be facing another in her next match.

The British teen beat 2011 French Open winner Li Na in the third round Friday, two days after she ended the career of four-time major champ Kim Clijsters. Next up: Sam Stosur, who happens to be the defending champion here.

"I have had a fairly tough draw, haven't I?" Robson said with the smile of a player racking up confidence.

Ranked 89th, Robson had never been past the second round of a major tournament or knocked off a top 10 opponent before this year's Open. Now she's done both, after eliminating the ninth-seeded Li 6-4, 6-7 (5), 6-2.

Robson put her hands to her head in 'I-can't-believe-this' joy after the Chinese star returned her serve long on the final point.

"I have had lots of tough matches against some very experienced opponents, so the way that I see it, it was time to start winning a few of them," she said.

Stretching before the match, Robson noticed a tweet from English football star Wayne Rooney wishing her luck. Except he called her "Laura Robinson." Rooney later faulted predictive text for the gaffe, which didn't seem to dent Robson's self-assurance.

"Can you blame that on predictive text, though?" she joked. "I'm not so sure."

Following her from the stands was British actor James Corden.

"I spotted him midway, like, first set, and then spent the rest of the time trying not to wave," Robson said.

She also showed poise after failing to close out the match in the second-set tiebreaker, then overcoming two incorrect calls in the third set where she had to replay points she would've won if the initial ruling had been right.

With a break point on Li's serve at 2-2 in the final set, Robson's return clipped the baseline and Li hit the ball wide. But the line judge called Robson's shot out and, after a review overturned it, Robson lost the replayed point. Li won the next point as well to earn game point. But with the Louis Armstrong Stadium crowd roaring its support, Robson rallied back to get the break.

"I was a little bit annoyed. But that's what happens from time to time, so you've got to deal with it," she said. "I think being a little bit annoyed seemed to help me, seeing as I broke the first game then I held serve the next time it happened."

On Wednesday, Robson ended Clijsters' career, winning both sets in tiebreakers in the second round against the 23rd-seeded Belgian. Robson's career may now be really getting started.

She became the next great British hope when she captured the 2008 Wimbledon girls title at age 14. Four years later, injury-free for the first time in a while, she seems to be reaching that potential, the youngest woman ranked in the top 100.

"I'm only 18, so if I was that negative a year ago, then who knows what I'm going to be like in a few years," Robson said, referring to whether she ever doubted her future.

"But, no, I have always thought that I can play with the top girls. Whenever I've practiced with, you know, Caroline or Maria, I've always felt that the level was there. It was just taking that onto the match court and keeping the level up for the whole match."

And she became the first British woman to make the fourth round at a Grand Slam event since Sam Smith at 1998 Wimbledon. Robson had 27 unforced errors to 34 by the 30-year-old Li.

"I was making a lot of mistakes in my whole match, so of course give a lot of free points to her," Li said. "Made her like, 'Oh, I got more confidence. Oh, I can beat her.' "

The seventh-seeded Stosur was pushed for the first time in this year's Open by No 31 seed American Varvara Lepchenko, but dominated the second set after winning the first in a tiebreaker for a 7-6 (5), 6-2 victory.

Stosur has never faced Robson - or really watched her play for long.

"She's obviously full of confidence and had two very, very good wins," Stosur said.

- AP