Top-ranked Sinner needed just an hour and 38 minutes to dispatch the 28-year-old Kopriva, who was appearing in the main draw at Flushing Meadows for the first time.

"It feels great to be back here. Obviously it's a very special tournament," said Sinner.

The Italian 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 defence of any Grand Slam tournament in the Open era.

Sinner, 24, next plays Alexei Popyrin or Emil Ruusuvuori for a place in the third round.

He appeared to be fully recovered from the illness that forced him to retire against Carlos Alcaraz in the Cincinnati Open final last week.

"I'm very happy that I'm healthy again," Sinner said after a clinical display in which he broke Kopriva seven times.

"We did our best to be in the best possible shape here. I'm very happy about today's performance."

"I have amazing memories (from last year). Every year is different. You come here starting this tournament hopefully in the best possible way, which I did."

Sinner has won two of this season's three Grand Slams, the Australian Open and Wimbledon, while also reaching the final of the French Open where he held three championship points before losing to Alcaraz in a fifth-set tie-break.

Swiatek swats Arango

Iga Swiatek launched her quest for a second US Open title with an emphatic victory on Tuesday.

Swiatek, the pre-tournament bookmakers' favourite following victories at Wimbledon and the Cincinnati Open, dispatched Colombia's Emiliana Arango in straight sets, winning 6-1, 6-2 on the Arthur Ashe Stadium court.

The 24-year-old Polish ace was always in control against 84th-ranked Arango, overwhelming the Colombian with some powerful groundstrokes mixed with some deft work at the net.

The win makes Swiatek the first woman in history to win 65 consecutive WTA-level first round games, surpassing Monica Seles' previous record of 64.

The six-time Grand Slam singles champion -- a winner in New York in 2022 -- will face either either Valerie Glozman of the United States or the Netherlands' Suzan Lamens in the second round.