Coco Gauff powered into the second round of the US Open on Monday, launching her title defence with a 6-2, 6-0 victory over Varvara Gracheva as defending men's champion Novak Djokovic prepared to start his repeat bid under the lights of Arthur Ashe Stadium.

Gauff, seeded third, 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.

"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."

Four-time champion Djokovic, seeded second behind world number one Jannik Sinner, is vying to become the first man to repeat in New York since Roger Federer won five straight US Opens from 2004-2008.

"Hopefully that changes this year," said Djokovic, who highlighted an otherwise disappointing season with an emotional gold medal at the Paris Olympics.

That victory satisfied a years' long quest for Djokovic, who has been hindered by a knee injury in 2024.

With Sinner and Carlos Alcaraz snapping at his heels, Djokovic is facing the prospect of a year without a Grand Slam title for the first time since 2017.

The 37-year-old, whose 24 Grand Slam titles are tied with Aussie legend Margaret Court for most all-time, says he still gets pumped up for the "pillars of our sport."

And that's especially true of the US Open, where he'll anchor the night session taking on Moldovan qualifier Radu Albot.

"I can't wait to be under the lights," Djokovic said. "The noise, the energy of the stadium is just different from anything else."

American Ben Shelton got the ball rolling 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."

- Krejcikova advances -

Fourth-seeded Alexander Zverev of Germany needed four sets to get past lucky loser Maximilian Marter 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.

Wimbledon women's 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.

"Every ball (from Anisimova) went inside in the beginning and I couldn't do anything," said Zheng.

"Little by little I started to get into the rhythm," added Zheng, who finished runner-up to Aryna Sabalenka at the Australian Open, and could face the second seed from Belarus in the quarter-finals.

Sabalenka closed out the night session on Louis Armstrong Stadium against Australian qualifier Priscilla Hon.