Make no mistake, President Donald Trump's spat with some of the most prominent sporting stars in America is not about patriotism, or even sport. Despite his protestations, it is about race.

American football is essentially a game played by black men for the entertainment of white men: 70 per cent of the top tier NFL players are African-American, 83 per cent of NFL fans are white and two-thirds of them are men.

None of the multi-millionaires and billionaires who own NFL franchises are black. And while most of those black NFL players are paid handsomely, it is becoming increasingly clear that many are paying a massive price with devastating injuries, including chronic traumatic encephalopathy which has driven dozens to early dementia or suicide.

The current dispute has its origins in a silent protest against the treatment of minorities in America by the quarterback of the San Francisco 49ers, Colin Kaepernick.

In August last year Kaepernick stayed in his seat while the rest of his team and the crowd rose to sing the national anthem before a pre-season game against the Green Bay Packers.

US President Donald Trump has been picking fights on Twitter with some high-profile athletes. ( Reuters: Kevin Lamarque )

"I am not going to stand up to show pride in a flag for a country that oppresses black people and people of colour," Kaepernick said at the time. "To me, this is bigger than football and it would be selfish on my part to look the other way.

"There are bodies in the street and people getting paid leave and getting away with murder."

His comments came after months of Black Lives Matter protests, in response to police shootings of black men in particular. Black people in America are three times as likely to be killed by police as white people, and five times as likely to be sent to prison.

Kneeling has caught on

Kaepernick's sit-down protest created a fierce debate at the height of the 2016 presidential election campaign that has continued ever since. He was accused of being unpatriotic, and disrespectful of Americans who have fought and died for their country.

Defenders said it was his free speech right, under the American constitution, to refuse to stand.

Colin Kaepernick kneels for the national anthem before a game in 2016. More than 100 players now follow suit. ( USA TODAY/Reuters: Kevin Hoffman )

In response to criticisms, Kaepernick modified his stance, to become a kneel, rather than a sit, which he saw as more deferential to veterans, some other players joined in and the controversy continued.

Kaepernick left the 49ers after last season, to become a "free agent" — making him able to sign with any team, free from the NFL drafting system, yet surprisingly no team has picked him up.

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Statisticians have concluded that reflects owners' concerns over bad PR rather than his performance.

With Kaepernick off the field, a few others continued to emulate his kneeling.

While sidelined, Kaepernick has continued to court controversy, likening police to the patrols once sent to recapture runaway slaves, and his partner Nessa Diab appeared to liken the owner of the Baltimore Ravens, who baulked at signing Kaepernick, to a slave owner.

Sorry, this video has expired Correspondent Zoe Daniel on the spat between Trump and NFL players (Photo: Reuters/Kirby Lee)

'Get that son of a bitch off the field'

At a rally in deep southern Alabama on Friday, Mr Trump told the crowd, "We're proud of our country, we respect our flag … Wouldn't you love to see one of these NFL owners, when somebody disrespects our flag, to say, 'Get that son of a bitch off the field right now, out, he's fired. He's fired!'"

Separately, one of America's top basketball players Steph Curry told reporters on Friday he didn't want to go to the White House on what has become a customary visit for the championship team. That prompted a rather petulant-sounding response on Twitter from the President, who withdrew the invitation.

Fellow basketballer Lebron James hit back on Twitter, calling the President a "bum" and pointing out that he couldn't disinvite Steph Curry, because he'd already said he wasn't going, and adding pointedly, "Going to the White House was a great honour until you showed up!"

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Picking a Twitter fight with some of America's best-known black athletes may not seem like the wisest move, so what is Mr Trump's end game?

Remember — 83 per cent of NFL fans are white. The President is calling for those mostly white fans to stop watching the NFL until all-white team owners bring their mostly black players into line, or fire them.

Owners back players, but do fans?

Unfortunately for Mr Trump, some of those team owners, including friends and supporters, think this time he's gone too far.

Robert Kraft of the New England Patriots defended the right of his players to "affect social change" and "raise awareness" and expressed "deep disappointment" in Mr Trump.

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The owners of the Cleveland Browns said the President's comments were "misguided, uninformed and divisive".

Buoyed by the support of their team owners, more than 100 football players in weekend games have emulated Colin Kaepernick's refusal to stand for the national anthem.

But Mr Trump remains, first and foremost, a populist with an uncanny ability to read the American mood (or at least an ability to read opinion polls).

Polls have shown 72 per cent of Americans think the Kaepernick kneel is "unpatriotic" and 61 per cent say they don't support his stance. But if you ask black Americans, only 11 per cent oppose Colin Kaepernick's protest.

Ratings for the NFL have fallen by double digits since 2016, and the most common reason given by fans for switching off was the national anthem protests over the way America treats minorities.

Yes, Mr President, this really is about race.