Novak Djokovic, fueled by an emotional Olympic triumph, has new Grand Slam records in his sights at the U.S. Open, where title rival Jannik Sinner hopes to shake off a doping controversy.

Defending champion Djokovic can become the oldest Open era champion at the tournament if he secures a fifth title, a record he would share with Jimmy Connors, Pete Sampras and Roger Federer.

The 37-year-old would also move to 25 Grand Slam triumphs, taking him clear of the 24 he currently shares with Margaret Court.

The final Grand Slam of the year comes at a critical time for Djokovic.

This year he was succeeded as Australian Open champion by Sinner who also relieved him of his world No. 1 ranking.

Carlos Alcaraz took his French Open title with the Spanish crowd-pleaser then sweeping Djokovic off court in a one-sided Wimbledon final.

However, Djokovic, returned to the clay courts of Roland Garros to stun Alcaraz in the Olympic final in what he Saturday called "the greatest achievement and greatest highlight of my career overall, winning the gold for Serbia."

Djokovic became just the fifth player to complete a career Golden Slam of all four majors and Olympic gold.

The victory also silenced the increasing number of doubters who had written off the Serb as a spent force in a new era where Sinner, 23, and 21-year-old Alcaraz are steadily moving center stage.

Djokovic, who underwent surgery on his right knee in June, said he wondered if his chances to win Olympic gold were running out.

"At 37 I thought, you know, I don't know, could this be the last chance? Maybe. So I had to push more than I have ever done," he said.

"Turned out to be one of the best performances I had in years overall throughout the entire tournament.

"Of course in the finals against Carlos, it was kind of a dream scenario really, having my wife and children there, the entire nation watching."

When they hung the gold around his neck and the Serbian anthem played, Djokovic said, it was "probably the most intense emotions I have ever had on a tennis court."

Sinner, meanwhile, arrives after an emotionally draining doping investigation, in which he escaped a lengthy ban after officials accepted his explanation that the banned substance entered his system as a result of contamination from a support team member.

The 23-year-old Italian had twice tested positive for clostebol, a banned anabolic agent, back in March. The International Tennis Integrity Agency announced this week he had been cleared of wrongdoing – a day after he won the Cincinnati Masters.

"I'm just happy that it's finally out," said Sinner, who fired his physiotherapist and trainer in the wake of the affair.

But his hopes for "clean air" at the US Open could be dashed as players question why there was never any announcement of a provisional suspension as the investigation proceeded.

Sinner said he wouldn't get caught up in concerns over his reputation.

"This, I can't really control," he said. "So let's see."

Alcaraz, who won his first major at the US Open in 2022, was badly bruised by his defeat to Djokovic in the Olympic final.

He broke down in tears on court and said he felt he had "let Spain down."

He lost his cool in a second-round exit at Cincinnati and tweaked an ankle in practice at Flushing Meadows, but insisted he'd be "100%" for his first-round match on Tuesday.

Defending women's champion Coco Gauff has endured a worrying dip in form in recent weeks, raising doubts over whether she could become the first woman since Serena Williams in 2014 to successfully defend her US Open crown.

A stormy third-round exit from the Olympics was followed by early defeats in Toronto and Cincinnati.

Five-time major winner and world No. 1 Iga Swiatek, the 2022 champion, made the Cincinnati semi-finals where she was defeated by Aryna Sabalenka.

Sabalenka, the Australian Open champion and runner-up to Gauff in New York last year, is another contender in a wide-open field that also features Wimbledon winner Barbora Krejcikova and Olympic gold medallist Zheng Qinwen.