US President Donald Trump has been booed loudly at the NBA finals in New York, which his home team went on to lose after a 13-game winning streak.

The crowd erupted in jeers when Trump was featured on the big screen during the national anthem before tip-off between the New York Knicks and San Antonio Spurs at Madison Square Gardens on Tuesday (AEST).

It was the first time a sitting president had been at an NBA final. The Knicks have not won a championship since 1973.

Later in the match Trump, a longtime Knicks fan, was filmed with his eyes closed, seemingly asleep, while around him the rowdy crowd reacted to the intense moments of the game.

The president’s appearance at Game 3 of the finals meant intense security protocols had to be enforced, with fans urged to arrive two hours early to undergo screening.

The Secret Service reportedly enforced a no-go zone for five blocks around Madison Square Garden, which was closed to vehicles and pedestrians.

Fans lined up to get inside the arena more than four hours before tipoff, in a scene more closely resembling New Year’s Eve in Times Square.

They were required to provide a ticket or pass to get past various checkpoints.

Social media footage showed chaos outside, with crowds of ticket-holders backed up for blocks as they waited to get inside for the anticipated match.

Secret Service personnel and police were positioned at every corner and in large numbers. Daily commuters, tourists visiting Manhattan and fans were all confounded at various times as they tried to manoeuvre the security.

Trump was watching from the MSG suite with his granddaughter Kai Trump and as a guest of Knicks owner James Dolan.

He performed a salute during the national anthem, but when his image was broadcast on the jumbotron, the stadium erupted in loud boos, although some whistles and cheers were audible.

He maintained the salute throughout the negative crowd reaction, which lasted about seven seconds before the video screens switched to footage of the players, which triggered cheers.

Some players acknowledged the impact of the president’s presence on the athletes as well as fans.

The Spur’s Victor Wembanyama goes through security. Photo: X

San Antonio Spurs guard De’Aaron Fox said Trump’s attendance made it “inconvenient on everybody else”.

“We got more, obviously, more security,” Fox told The Athletic.

“We’re getting screened like it’s TSA. It’s a little inconvenient for the people that’s gotta play, but it is what it is.”

Sports presenter Stephen A Smith said it would be the president’s fault if the Knicks lost.

“If it causes the Knicks to lose tonight, I’m blaming him. I’m blaming the president of the U.S.

“Damnit, I hope the GOP loses votes because of it if we lose tonight.”

Before the game, NBA Commissioner Adam Silver said Trump was “a genuine Knicks fan”.

Trump’s Marine One helicopter flew from his home in New Jersey and landed near Wall Street before his motorcade made its way up through Manhattan and to the arena roughly an hour before tipoff.

He encountered a handful of people making rude gestures, and outside the area, one group held signs saying “Trump must go.”

Before his time in politics, Trump frequently attended Knicks games and often sat courtside.

New York had won 13 straight games until Tuesday, the second-longest streak by any team in NBA playoff history.

Other celebrities in the audience were Ben Stiller, Timothee Chalamet, and Pete Davidson.

-with AAP