New York, Sep 7 (AP) President Donald Trump attended the US Open on Sunday and briefly stepped out from a luxury box to wave at a main court crowd mostly still arriving for the men's final. He drew mixed cheers and boos.

Arthur Ashe stadium was only partially full and Trump's waves weren't announced beforehand. They were also brief enough so that some of those in attendance didn't notice them.

The president attended as a guest of Rolex despite imposing steep tariffs on the Swiss watchmaker's home country, and organisers were seeking to keep booing of him from being seen on the TV broadcast.

Trump has built the bulk of his second term's domestic travel around attending major sports events rather than hitting the road to make policy announcements or address the kind of large rallies he so relished as a candidate.

Because of extra security screening, the final between second-seeded Carlos Alcaraz, a 22-year-old Spaniard, and No. 1 seed and defending champion Jannik Sinner, 24, of Italy, was pushed back half an hour — meaning Trump arrived more than 45 minutes before the new start time.

The president was watching from Rolex's suite, and his acceptance of Rolex's invitation comes mere weeks after the Trump administration imposed a whopping 39 per cent tariff on Swiss products.

The levy is more than 2 1/2 times higher than the one the Trump administration agreed to for European Union goods exported to the US and nearly four times higher than on British exports to the US. It has raised questions about Switzerland's ability to compete with the 27-member bloc that it neighbours.

The White House declined to comment on Trump accepting a corporate client's invitation at the tournament, but the president has had few qualms about blurring lines between political and foreign policy decisions and efforts to boost the profits of his family business.

That includes tirelessly promoting cryptocurrency interests and luxury golf properties around the country and the world that bear his name. He announced Friday that the US will use its turn hosting the Group of 20 summit in December 2026 to stage the sweeping event at Trump National Doral in South Florida.

Any negative reaction to Trump's presence won't be shown on ABC's national telecast, per standard policy, the US Tennis Association says.

“We regularly ask our broadcasters to refrain from showcasing off-court disruptions,” the organisation said in a statement.

As heavy rains began mostly clearing, and throngs of fans arrived for the match, no major street protests against the president could be seen from the touranment's main stadium. Attendees also steered clear of wearing any of the president's signature “Make America Great Again” caps, though.

A 58-year tennis fan originally from Turin, Italy, came from her home in the Boston area to watch the final and said that when she bought a US Open cap, she went with a fuchsia-hued one so it wouldn't be mistaken for the signature darker color of MAGA hats.

“I was careful not to get the red one,” said the fan, who declined to give her name because of her employer's rules about being publicly quoted.

Attending with Trump were White House press secretary Karoline Leavitt, Attorney General Pam Bondi, Treasury Secretary Scott Bessent, special administration envoy Steve Witkoff and Susie Wiles, the White House chief of staff.

Elsewhere in the crowd were a slew of celebrities — some of whom publicly backed then-Vice President Kamala Harris during last year's election against Trump. Among them were Pink, Bruce Springsteen, Shonda Rhimes, Michael J. Fox, Sting, Shaggy, Ben Stiller and Courtney Cox.

Trump came back to the press cabin on Air Force One during the flight to New York to note that the plane would be flying over Ashe stadium, but didn't offer any further comment.

Trump was once a US Open mainstay, but hasn't attended since he was loudly booed at a quarterfinals match in September 2015, months after launching his first presidential campaign.

The Trump Organisation once controlled its own US Open suite, which was adjacent to the stadium's television broadcasting booth, but suspended it in 2017, during the first year of Trump's first term. The family business is now being run by Trump's sons with their father back in the White House.

Trump was born in Queens, home of the US Open, and for decades was a New York-area real estate mogul and, later, a reality TV star. Attending the tournament before he was a politician, he usually sat in the suite's balcony during night matches and was frequently shown on the arena's video screens.

In recent years, however, including between his presidential terms, Trump primarily lived at his Florida estate, Mar-a-Lago.

Alcaraz said before the final that having Trump on-hand would be a privilege and “great for tennis,” but also suggested that such sentiment went for any president watching from the stands. “I don't want myself to be nervous because of it," he said.

The president has also frequently attended sporting events — where the roar of the crowd sometimes features people booing him while others cheer him.

Since returning to the White House in January and prior to Sunday's US Open swing, Trump went to the Super Bowl in New Orleans and the Daytona 500, as well as UFC fights in Miami and Newark, New Jersey, the NCAA wrestling championships in Philadelphia and the FIFA Club World Cup final in East Rutherford, New Jersey.

Having a sitting president attend the US Open hasn't happened since Bill Clinton went to the 2000 tournament, though former President Barack Obama and his wife, Michelle, attended the event's opening night in 2023. (AP) GSP

Conflict of interest flagged as president accepts corporate hospitality from a Swiss firm amid steep US tariffs. President attended a major sporting event as a corporate guest of a Swiss watchmaker while his administration had recently imposed steep tariffs on Swiss goods, prompting scrutiny of a possible conflict of interest in accepting hospitality from a party affected by US trade policy; organisers and broadcasters sought to limit televised depiction of crowd booing, and the White House declined to comment on the invitation's propriety.