Sports stars and athletes around the world have defied US President Donald Trump’s demands for football players who kneel during the national anthem to be sacked or suspended by the country’s National Football League (NFL).

At matches on Sunday, more than 100 NFL players sat or knelt – the form of protest started last season by former San Francisco 49ers quarterback Colin Kaepernick, who was campaigning against what he saw as civil rights abuses in the United States.

Most teams in the early afternoon games locked arms in solidarity, with at least three team owners joining their players.

And in what appeared to be an astonishing gesture of solidarity, Australian tennis player Nick Kyrgios also joined in, kneeling before the coin toss at the Laver Cup in Prague, in the Czech Republic.

Nick Kyrgios before the match in Prague. Photo: Twitter

Kyrgios later claimed the gesture had nothing to do with Mr Trump’s politics or the NFL players’ protest, and was a mark of respect for his late grandparents.

In London, at the exhibition game between the Baltimore Ravens and the Jacksonville Jaguars, about two dozen players knelt during the US national anthem before the start of the game at Wembley Stadium.

No players knelt during the playing of the British national anthem, God Save the Queen.

The protest is part of a bitter war of words between the President and US sports teams, which sparked a flurry of angry tweets over the weekend, even urging fans to boycott games in response to players’ defiance.

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!

— Donald J. Trump (@realDonaldTrump) September 24, 2017

Mr Trump then urged the NFL to back his demands for players to desist.

…NFL attendance and ratings are WAY DOWN. Boring games yes, but many stay away because they love our country. League should back U.S.

— Donald J. Trump (@realDonaldTrump) September 24, 2017

The tweets came after a spat between the President and basketball stars LeBron James and Stephen Curry over their reticence to accept an invitation to the White House, with James ultimately branding the President a “bum”.

Mr Trump announced that Curry, the popular two-time most-valuable basketball player for the Golden State Warriors, would not be welcome at the White House for the commemorative visit traditionally made by championship teams.

Curry had said he didn’t want to go to the White House in any case, but the Warriors had not made a collective decision before Saturday.

Meanwhile, one NFL team, the Pittsburgh Steelers remained in the locker room as the national anthem played before their game with the Chicago Bears, while their coach Mike Tomlin stood by himself on the sideline.

Tomlin had said before the game that “we’re not going to let divisive times or divisive individuals affect our agenda”.

On Saturday, Mr Trump said players who take a knee during the national anthem should be fired.

“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’,” Mr Trump said to loud applause Friday night at a rally in Huntsville, Alabama.

Players and owners united in defiance of Mr Trump.

New England Patriots owner Robert Kraft, who’s been a strong supporter of the President, expressed “deep disappointment” with Mr Trump.

“I am deeply disappointed by the tone of the comments made by the President,” Mr Kraft said in a statement.

“Our players are intelligent, thoughtful, and care deeply about our community and I support their right to peacefully affect social change and raise awareness in a manner that they feel is most impactful.”

Green Bay Packers President and CEO Mark Murphy also condemned Mr Trump and backed any players who opted to kneel for the anthem.

“We believe it is important to support any of our players who choose to peacefully express themselves with the hope of change for good. As Americans, we are fortunate to be able to speak openly and freely,” Mr Murphy said.

– with AAP