SOMERSET, N.J.,/WASHINGTON (Reuters) – National Football League players sat out, knelt and linked arms during pre-game national anthems played across the country and in London on Sunday, hours after U.S. President Donald Trump called on fans to boycott teams that do not discipline players who protest.

In the first few games since Trump stepped up his criticism of NFL players, dozens of players and coaches of teams including the Baltimore Ravens, Jacksonville Jaguars, Philadelphia Eagles and Miami Dolphins did not stand for the anthem and took a knee, a gesture that began last year as a protest over police treatment of African-Americans and other minorities.

The Pittsburgh Steelers waited off the field during the national anthem before their game against the Chicago Bears in Chicago to avoid “playing politics” in divisive times, coach Mike Tomlin said.

In Detroit, several members of the Lions knelt while singer Rico Lavelle dropped to one knee and pumped a fist in the air at the end of his performance of the national anthem.

And in Philadelphia, city police officers joined with Eagles and rival New York Giants players and Eagles team owner Jeffrey Lurie to link arms during the anthem in a sign of solidarity.

Trump made a series of comments over the weekend criticizing players who refuse to stand for the national anthem.

“If NFL fans refuse to go to games until players stop disrespecting our Flag & Country, you will see change take place fast,” Trump wrote on Sunday morning on Twitter. “Fire or suspend!”

In another tweet, Trump, who is spending the weekend at his golf club in Bedminster, New Jersey, said that the “league should back” fans who are upset about the protests.

The form of protest began in 2016 when then San Francisco 49ers quarterback Colin Kaepernick put one knee to the ground during pre-game renditions of the “Star Spangled Banner.” Several players have since made similar gestures.

Kaepernick initially started his protests last year by sitting during the anthem but when critics said it was a sign of disrespect, he instead took to kneeling.

At a political rally on Friday in support of his favored Senate candidate in a special election in Alabama, Trump suggested any protesting football player was a “son of a bitch” and should lose his job.

The comments criticizing African-American athletes, who are taking a stand against institutional racism and inequality, stirred up Trump’s conservative base as he grapples with North Korea’s nuclear threats, an investigation of Russian meddling in the 2016 U.S. election and ties to Trump associates while also struggling for a legislative win on healthcare in Congress.

As the NFL community began to speak out against Trump’s comments on Sunday, including people he considers friends and allies, Trump took to Twitter again on Sunday afternoon.

“Great solidarity for our National Anthem and for our Country. Standing with locked arms is good, kneeling is not acceptable. Bad ratings!” he wrote.

In a follow-up Tweet, Trump announced that the Pittsburgh Penguins hockey team, which won the Stanley Cup, accepted his invitation to the White House. “Great team!” he wrote.

DEFYING TRUMP

On Sunday morning, NFL managers, coaches and owners began to weigh in on the feud, criticizing the president for calling out players’ political dissent.

New England Patriots Chairman and CEO Robert Kraft, who has dined with Trump and who the president considers a friend, criticized Trump and defended players’ right to protest.

“I am deeply disappointed by the tone of the comments made by the president on Friday,” Kraft said in a statement. Kraft said he supports his players’ “right to peacefully affect social change and raise awareness in a manner they feel is most impactful.”

Over a dozen Patriots players and coaches knelt or linked arms, including quarterback Tom Brady, who Trump had namedropped as a friend when he was on the campaign trail. Brady placed one hand on his chest and used the other to link arms with his teammates.

Jaguars owner Shad Khan linked arms with team players in solidarity at the game against the Ravens in London’s Wembley Stadium. Khan donated $1 million to the Trump inauguration fund.

And Robert McNair, chairman of the Houston Texans team, said Trump’s comments were “divisive and counterproductive to what our country needs right now.” McNair also donated $1 million to Trump.

NFL Commissioner Roger Goodell said Trump’s comments in Alabama revealed an “unfortunate lack of respect” for the NFL and its players.

As commissioner, Goodell reports to NFL owners, some of whom have supported Trump. New York Jets owner Woody Johnson, a major Trump presidential campaign donor, was confirmed by the Senate last month as Trump’s pick to serve as U.S. ambassador to Britain.

The union representing professional football players also rejected Trump’s comments, saying it would defend their right to freedom of expression.

In Chicago, Trump’s feud was the main topic of conversation at the South Loop Club sports bar.

“This is a first amendment issue and the president is supposed to uphold that right,” said Sam Cunningham, 55, who was watching the Pittsburgh-Chicago game with his wife. “He should know better than anyone that to fire someone because of their opinion is not right.”

One patron at a sports bar in Fort Lauderdale, Florida, Trump supporter Tim Kull, 67, said: “Do it on your time, not when you are wearing that uniform.”

National Basketball Association players also struck back against comments by the president on Saturday after Trump clashed with one of the biggest stars in the NBA, Stephen Curry. Then on Saturday evening, Oakland As rookie Bruce Maxwell became the first Major League Baseball player to kneel for the national anthem in protest.

In a Twitter message, Trump rescinded a White House invitation to Curry, who had said he would “vote” against the planned visit by the NBA champion Golden State Warriors.

Curry told a news conference in Oakland, California: “It’s beneath the leader of a country to go that route.”

Singer Stevie Wonder also appeared to evoke protests by Kaepernick and other athletes when he put one knee to the stage during a concert in New York on Saturday.