Defending champion Novak Djokovic eased into the second round of the US Open with a straight-sets victory over qualifier Radu Albot on Monday as Coco Gauff launched her defence of the women's title with a convincing victory.

Djokovic, seeking his 25th Grand Slam title and his first since his victory at Flushing Meadows last year, wasn't his sharpest self.

But he was more than a match for 138th-ranked Albot, breaking the Moldovan six times on the way to a 6-2, 6-2, 6-4 victory.

He notched a men's record 78th match win on Arthur Ashe Stadium, where he said the "electric" energy of the night session was unlike any other.

"The night sessions here are best in the world," said Djokovic, who capped the action on a day that drew a record 74,641 spectators according to the US Tennis Association.

That included a day-session crowd of 42,886 and a record-setting night-session crowd of 31,775.

"There's an incredible energy, and with the new rule this year that the crowd can move around, there are a lot of things happening," the four-time champion said.

Seeded second behind Jannik Sinner, Djokovic is vying to become the first man to repeat in New York since Roger Federer won five straight US Opens from 2004-2008.

He's coming off an emotional triumph at the Paris Olympics, but Djokovic has yet to capture a Grand Slam title this year.

He had 10 double faults among 40 unforced errors, but was nevertheless in full control throughout the two hour, seven minute contest that ended shortly before midnight.

Gauff, meanwhile, powered into the second round with a 6-2, 6-0 victory over France's Varvara Gracheva.

The 20-year-old American fired 10 aces and needed just 66 minutes to beat 66th-ranked Gracheva. She saved eight break points -- including two with aces in the final game.

"It is definitely a lot of pressure this tournament but I'm just enjoying it," said Gauff, who is seeded third behind world number one Iga Swiatek and Aryna Sabalenka.

"Last year was incredible, so I'm just bringing those vibes and whatever happens, happens."

Gauff has battled through an erratic season since capturing her maiden major last year and her tune-up tournaments saw her fall in the third round at Toronto before she crashed out of her first match as the defending champion in Cincinnati.

- A little tough -

"The last few weeks have been a little bit tough," Gauff said. "But today was I think the best tennis I've played in a while."

American Ben Shelton opened the action on Ashe with a 6-4, 6-2, 6-2 victory over 2020 champion Dominic Thiem.

Shelton's triumph marked an end to Thiem's Grand Slam career, the Austrian having announced he would retire at the end of 2024 after several injury-plagued seasons.

"I just want to say thanks for all the support," Thiem told fans. "It's been 10 years since I first played here, I had my greatest success on this court."

Fourth-seeded Alexander Zverev of Germany needed four sets to get past lucky loser Maximilian Marterer 6-2, 6-7 (5/7), 6-3, 6-2.

Sixth-seeded Andrey Rublev beat Brazilian Thiago Seyboth Wild 6-3, 7-6 (7/3), 7-5 and eighth-seeded Casper Ruud of Norway advanced with a 7-6 (7/2), 6-2, 6-2 win over China's Bu Yunchaokete.

Ruud next faces French veteran Gael Monfils, who beat Diego Schwartzman 6-7 (2/7), 6-2, 6-2, 6-1 in the Argentinian's final Grand Slam appearance as he heads into retirement.

Australian Open champion Aryna Sabalenka cruised into the second round with a 6-3, 6-3 victory over Australian qualifier Priscilla Hon.

Wimbledon champion Barbora Krejcikova, seeded eighth, eased into the second round with a 7-6 (7/3), 6-2 victory over Spanish qualifier Marina Bassols Ribera.

Olympic women's singles gold medallist Zheng Qinwen of China, seeded seventh, rallied from a set down to beat Amanda Anisimova 4-6, 6-4, 6-2.