At least 100 American football players have used the national anthem to show their defiance to President Donald Trump’s criticism, by kneeling or sitting in protest.
The owners of two leading team also joined a chorus of NFL executives criticising President Trump’s suggestion that they fire players who kneel for the national anthem.
The statements – from New England Patriots owner Robert Kraft and Baltimore Ravens owner Steve Bisciotti – followed another controversial morning tweet from Mr Trump.
Most teams in Sunday afternoon’s games locked arms in solidarity and at least three team owners joined their players.
More than 100 players sat or knelt, the form of protest against the treatment of black people by police started last season by former San Francisco 49ers quarterback Colin Kaepernick.
Mr Kaepernick is now a free agent and supporters believe teams have avoided signing him because of his protest.
The Pittsburgh Steelers remained in the locker room as the national anthem played before their game with the Chicago Bears. Coach Mike Tomlin stood by himself on the sideline.
Mr Tomlin had said before the game that Pittsburgh’s players would remain in the locker room and “we’re not going to let divisive times or divisive individuals affect our agenda.”
Ravens owner Mr Bisciotti said he “100%” supports his players’ decision to kneel during the national anthem.
At least seven of them did, joined by more than a dozen Jacksonville Jaguars, before the teams played at Wembley Stadium in London.
Patriots owner Mr Kraft, who has been a strong backer of the president, expressed “deep disappointment” with Mr Trump and said politicians could learn much from the unifying spirit of a competitive, team-oriented enterprise like football.
Without identifying Mr Kaepernick, Mr Trump aimed a Friday speech at a Huntsville, Alabama, rally at those players who have knelt for the anthem.
“Wouldn’t you love to see one of these NFL owners, when somebody disrespects our flag, you’d say, ‘Get that son of a bitch off the field right now. Out! He’s fired,’” he said to loud applause.
In a Sunday-morning tweet, Mr Trump urged his supporters to take action: “If NFL fans refuse to go to games until players stop disrespecting our Flag & Country, you will see change take place fast. Fire or suspend!”
Treasury Secretary Steve Mnuchin followed up on ABC’s This Week defending Mr Trump, saying the NFL has many rules governing what players can and cannot do.
“I think what the president is saying is that the owners should have a rule that players should have to stand in respect for the national anthem,” Mr Mnuchin said.
“They can do free speech on their own time.”