World number one Jannik Sinner dropped only four games in a dominant straight-set win over Vit Kopriva in the first round of the US Open.

The defending champion wrapped up a 6-1, 6-1, 6-2 victory over Czech player Kopriva, ranked 89th in the world, in an hour and 38 minutes on Arthur Ashe Stadium.

Most notably, the 24-year-old Italian showed little sign of the illness which forced him to retire early from his Cincinnati Open final against Carlos Alcaraz last week.

"I'm very happy that I'm healthy again and that we did our best to be in the best possible shape here," Sinner said after his win.

Kopriva, making his main-draw debut in New York, failed to pose any serious threat to Sinner, who has now won 22 consecutive matches at hard-court Grand Slams.

The Italian has won three of the past four majors, having followed last year's US Open success with victories at January's Australian Open and at Wimbledon last month.

Sinner's only Grand Slam loss so far this year was to Spaniard Alcaraz in an epic French Open final in June.

"I have amazing memories," said Sinner, when asked about returning to Flushing Meadows as defending champion.

"Every year is different and you come here starting this tournament hopefully in the best possible way, which I have done.

"Coming back to a Grand Slam, where the emotions are still running - I'm very happy to come back here and compete against the best players in the world."

Sinner's second-round opponent will be Australia's world number 36 Alexei Popyrin, who defeated Emil Ruusuvuori of Finland in straight sets.

Elsewhere in the men's singles first round, Sinner's compatriot Lorenzo Musetti beat big-serving Frenchman Giovanni Mpetshi Perricard 6-7 (3-7) 6-3 6-4 6-4.

The Italian 10th seed lost the first set on a tie-break but did not face a break point as he registered only his second match win since retiring injured from his French Open semi-final against Alcaraz in June.

Kazakhstan's 23rd seed Alexander Bublik beat veteran Croat and 2014 US Open champion Marin Cilic 6-4 6-1 6-4, while Denis Shapovalov, the 27th seed from Canada, was a 6-0 6-4 6-4 winner against Hungary's Marton Fucsovics.