The 2019 champion is looking strong again in New York after a 6-1 6-2 victory.
Bianca Andreescu made it a perfect 10 at the US Open with a dominant victory over Greet Minnen to reach the fourth round.
The Canadian won her maiden grand slam title on her debut at Flushing Meadows in 2019 and, after not defending it last year, has added another three victories to maintain her hopes of a second title.
After a long battle against Viktorija Golubic in round one, Andreescu has looked more and more impressive, and she raced to a 6-1 6-2 success against Belgian Minnen.
“I think I played really well today,” said the 21-year-old, the momentum of whose remarkable 2019 breakthrough was stalled by injuries and the coronavirus pandemic.
“This is what I have been working towards in practice, and I’m very pleased with my return games, with my service games, with my movement on court, also with my attitude.
“I hope that it can continue like this the whole way and I can be 14-0 at the US Open. That’s my goal.”
Olympic gold medallist Belinda Bencic continued her fine summer with a 6-2 6-4 victory against American Jessica Pegula.