NEW YORK (AFP) — Reigning men’s champion Jannik Sinner charged into the third round of the US Open on Thursday as Coco Gauff and Iga Swiatek battled to keep their title bids intact.

Sinner swatted Australia’s Alexei Popyrin aside 6-3, 6-2, 6-2 to stretch his Grand Slam winning streak on hard courts to 23 matches.

The Italian top seed has made a convincing start in his bid to become the first man to repeat as US Open champion since Roger Federer won five in a row from 2004-2008.

“I’m very happy that I managed these matches as good as I could,” said Sinner, who dropped only four games in his opening win before blasting past the 36th-ranked Popyrin.

“I am aiming to improve on the serve but the rest (of my game) I am quite comfortable with.”

Sinner faces Canadian 27th seed Denis Shapovalov in the third round on Saturday.

He has reached the final of all three Grand Slams this season, winning the Australian Open and Wimbledon either side of a defeat to Carlos Alcaraz at the French Open.

Third seed Alexander Zverev cruised to a 6-4, 6-4, 6-4 win over Britain’s Jacob Fearnley, while Lorenzo Musetti eased 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.

“It’s literally something that I’ve dreamed of, that I think every tennis player dreams of — to keep going in a Slam,” Wong said.

Karen Khachanov became the biggest casualty so far in the men’s draw as the Russian ninth seed blew a two-set lead in his loss to Poland’s Kamil Majchrzak.

Gauff displayed great resolve to overcome another shaky performance that reduced her to tears in the night session on Arthur Ashe.

Third seed Gauff shrugged off Croatia’s Donna Vekic 7-6 (7/5), 6-2 despite being broken four times in the opening set as her serving woes resurfaced.

“Honestly, today was a tough match for me, but I’m just happy with how I was able to manage it,” said Gauff, choking back tears. “It’s been a rough couple of weeks.”

“I was just trying to tell myself to breathe, just put another ball in the court and keep doing the things that I do well,” she added.

Gauff drew inspiration from the presence of gymnastics icon Simone Biles as she hauled herself out of trouble.

“I was just thinking if she can go on a six-inch wide beam and perform with all the things she’s gone through, I can come out here on court and hit a ball,” Gauff said.