Maria Sharapova has fought off the challenge of American teenager Sofia Kenin to reach the fourth round of the US Open with a 7-5 6-2 victory.

After three-set struggles against Simona Halep and Timea Babos in earlier rounds, this was slightly more comfortable for Sharapova.

The five-time grand slam champion next plays 16th seed Anastasija Sevastova.

“We’ve never faced off against each other before, she’s up and coming, she had nothing to lose and that’s always dangerous. I’m really glad I came through,” Sharapova said.

“I didn’t see the ball too well at the beginning, made a lot of unforced errors. But ultimately what matters is I won and I get the chance to go to the practice court tomorrow and regroup.”

Playing her third match on Flushing Meadows’ centre court and second in the prime-time night session, Sharapova did not have the crowd with her this time as they got behind Kenin.

The Russian-born teenager had never won a grand slam match before this week and, unless she turns professional immediately, will have to forfeit her $US144,000 in prize money.

Kenin was outmatched physically but fought doggedly to stay with Sharapova and a slew of unforced errors from the Russian saw her pegged back from 4-1 to 4-4.

As she had against Babos, Sharapova struggled to produce the free-swinging tennis that stunned Halep, but she played two fine points to clinch the opening set.

There was a blip in the second set when Sharapova double-faulted to go from 3-0 to 3-2 but she then reeled off another three games to book her spot in the last 16.

—AAP