Donald Trump has praised fans who booed the Dallas Cowboys for kneeling before the national anthem, lauding their “great anger”.
The team’s players, coaches, and owner Jerry Jones all knelt on the field ahead of the national anthem, before rising for The Star-Spangled Banner.
There were numerous boos from the Monday night crowd at the University of Phoenix Stadium in Arizona.
It comes after more than 200 players knelt, sat or prayed during the national anthem at the weekend, something the US President has said should result in them being fired.
Mr Trump’s rhetoric has been condemned by players, owners and NFL sponsors.
The protests started more than a year ago when former San Francisco 49ers quarterback Colin Kaepernick refused to stand during the national anthem as a protest over police treatment of minorities.
Reacting to events in Arizona on Monday night in a series of tweets, Mr Trump said ratings for the NFL were “way down”, except before the games kick off “when people tune in to see whether or not our country will be disrespected!”
The President claimed the booing was the “loudest I have ever heard” and ended his second message with: “Great anger.”
He then added: “But while Dallas dropped to its knees as a team, they all stood up for our National Anthem. Big progress being made-we all love our country!”
Cowboys’ owner Jerry Jones has been a staunch supporter of the President and there was speculation that he would not allow his players to kneel during the national anthem.
“I hope that I’m clear and I hope that our team is clear: We want to respect the flag. Make no mistake about that,” Mr Jones said.
“Nothing that we’ve done, nothing that we did tonight says anything other than that.
“We also want to as a complete team, as players and an organisation, be able to, whenever we can, demonstrate that unity is important and equality is important.
“That’s what I’m so proud of these guys for, they did both and did it in a way when people really stop and think about it, makes a lot of sense.”
The Cowboys’ opponents, the Arizona Cardinals, gathered along the goal line arm-in-arm during the anthem. They were joined by owner Michael Bidwell, his family and general manager Steve Keim.
Several NFL sponsors have backed the players’ right to protest.
Nike said in a statement it “supports athletes and their right to freedom of expression on issues that are of great importance to our society”, while Hyundai said: “We stand for and respect individuals’ freedoms to express their First Amendment rights in any peaceful manner in which they choose.”