Journalist Ben Rothenberg posted on X: “Ooh, #USOpen just showed Trump on screen again during this set break and there was loud, clear booing this time.”

After delays, Alcaraz took the lead first on Sunday afternoon, winning the first set 6-2 in 37 minutes.

Sinner, 24, is defending his 2024 U.S. Open win against rival Alcaraz, 22, in a repeat of this year’s final matches of the French Open and Wimbledon—Alcaraz won their French Open match in June, while Sinner triumphed at Wimbledon in July.

Trump is attending as a guest of luxury Swiss watchmaker Rolex—a company facing a steep 39% tariff the Trump administration levied on imports from the European nation earlier this year.