Iga Swiatek scrapped her way into the third round of the US Open on Thursday with a three-set win over Suzan Lamens as Jannik Sinner sought to keep his title defense on track.

World number two Swiatek looked to be cruising as she led her Dutch opponent by a set and a break but stumbled before eventually seeing off the 66th-ranked Lamens 6-1, 4-6, 6-4.

"It wasn't an easy match. I did some mistakes," said Swiatek.

"I felt like it depended on me and if I made mistakes or not, sometimes I did. I probably got a little tight in the second set.

"But the third set is a reset. You've got to start from the beginning and I knew I could play a little more precisely, so I just tried to do that."

Swiatek, the 2022 US Open champion, has won 16 of 17 matches following titles at Wimbledon and Cincinnati. She goes on to play Russian 29th seed Anna Kalinskaya for a spot in the last 16.

Ekaterina Alexandrova, Beatriz Haddad Maia and Linda Noskova were among other women's seeds to advance.

Sinner is back in action later on Thursday as he takes on Alexei Popyrin, the Australian who inflicted a shock defeat on Novak Djokovic at last year's tournament.

The Italian has won his last 22 matches on hard courts at Grand Slams and said he felt fully healthy again after dealing with illness last week in Cincinnati.

He is trying to become the first man to repeat as US Open champion since Roger Federer won five in a row from 2004-2008.

It is the longest run without a successful men's title defense of any Grand Slam tournament in the Open era. 

Sinner will be hoping to join Lorenzo Musetti in the next round. The Italian 10th seed matched his best US Open run as he blew past Belgium's David Goffin.

Russian 15th seed Andrey Rublev beat American wild card Tristan Boyer in four sets. He advances to a last-32 tie with Hong Kong's Coleman Wong.

Wong, a 21-year-old qualifier, extended his New York fairytale with a 7-6 (7/5), 6-2, 4-6, 6-4 win over Australian Adam Walton.

The 173rd-ranked Wong had already made history earlier in the week by becoming the first man from Hong Kong to win a Grand Slam singles match.

Alexander Zverev plays Britain's Jacob Fearnley after Coco Gauff kicks off the night session on Arthur Ashe against Croatia's Donna Vekic.

The third-seeded Gauff stumbled through her opening match and admitted the build-up to the tournament had been "mentally exhausting" after shaking up her coaching team.

Twice former US Open champion Naomi Osaka takes on American Hailey Baptiste after making an encouraging start in her first Grand Slam as a seeded player since 2022.

Wimbledon runner-up and eighth seed Amanda Anisimova plays 19-year-old Australian Maya Joint under the lights on Louis Armstrong.

by Martyn WOOD