PHOTOS: Djokovic speeds into third round, Li avenges loss to Robson

Top-seeded Novak Djokovic saved two set points in the opening set but lost just four games the rest of the way in beating Germany's Benjamin Becker 7-6 (2), 6-2, 6-2 to reach the third round of the US Open on Friday.

Djokovic was broken in the ninth game of the first set to fall behind 4-5, but broke right back and forced a tiebreaker, which he won 7-2 before cruising the rest of the way.

After the 52-minute first-set struggle on a windy Arthur Ashe Stadium court, the Serb won the next two sets in a total of 59 minutes to seal his victory.

Australia Open champion Djokovic, the 2011 US Open winner, will next face either Finland's Jarkko Nieminen or Portugal's Joao Sousa.

China's Li Na became the first player to reach the round of 16 at this year's US Open when she defeated Britain's Laura Robson 6-2, 7-5 on Friday.

Li needed just 81 minutes to avenge her third round loss to Robson at Flushing Meadows last year and is yet to drop a set in the tournament.

"At least this year I'm in the second week," said Li, whose next opponent will be either Serbia's Jelena Jankovic or Japan's Kurumi Nara.

As a former French Open champion and two-time Australian Open finalist, Li had too much experience and firepower for the British teenager, 12 years her junior.

The 31-year-old Li was rewarded for her aggressive approach, hitting 23 winners and banging down 11 aces on a windy day at Arthur Ashe Stadium.

"I was a little bit surprised because today I have a lot of aces. It was like, wow." Li said.

Laura Robson contributed to her own downfall by committing 30 unforced errors, 15 in each set, but was satisfied with her overall performance in the tournament.

"I'm disappointed about today for sure and I thought I could have played a lot better," she said. "But I always knew it was going to be a tough match. All in all, I guess it was an average week.

"In my first two rounds I thought I played really well and I closed out the matches really well, which is something that has improved a lot over the last 12 months."

Still just 19, Robson is making steady improvement each season and was the first British woman to be seeded at a Grand Slam in more than a quarter of a century.

"I think I'm going in the right direction. I feel like I'm improving and working on a more all-around game," she said.

"It's going to take a lot of hard work, but I'm willing to do that."

The ultra-consistent Agnieszka Radwanska wore down Russia's Anastasia Pavlyuchenkova 6-4, 7-6 (1) to reach the fourth round at the US Open, continuing her impressive streak at this year's Grand Slams.

The third seeded Radwanksa survived some anxious moments against Pavlyuchenkova before sealing victory in 73 minutes.

She will play Sabine Lisicki or Ekaterina Makarova in the round of 16.

If she wins her next match, the Pole will become the only woman to reach the quarter-finals at all four Grand Slams this year.