Trump fields criticism, continues to attack NFL on Twitter

US President Donald Trump denied inflaming racial tensions Monday, insisting his charged comments that prompted protests by NFL and other players were about patriotism, not colour.

After his volley of verbal attacks on black athletes led players across the country to kneel during the US national anthem over the weekend, the besieged president played defence on Twitter on Monday.

'He's fired!'

Trump had started the furore by attacking players like Colin Kaepernick. The NFL player first took a knee through renditions of the Star-Spangled Banner during last year's American football season to protest police brutality toward African-Americans. 

Trump indirectly called Kaepernick a "son of a bitch" who should be fired.

More than 150 pro-football players took a defiant stance on Sunday, kneeling, linking arms or raising clenched fists during the anthem before 14 games.

In response, the US leader doubled down on those remarks by urging fans to boycott the NFL as long as the protests continued.

And on Monday, keeping the issue alive for the fourth day, Trump insisted: "The issue of kneeling has nothing to do with race. It is about respect for our Country, Flag and National Anthem. NFL must respect this!"

He also took to Twitter to deny any rifts about the issue with his influential chief of staff.

Troubling time for Trump

Trump – who faces low poll numbers and is struggling to enact his agenda – earlier tried to single out the NFL players who protested.

"Many people booed the players who kneeled yesterday (which was a small percentage of total). These are fans who demand respect for our Flag!" he tweeted.

The White House denied that Trump's "son of a bitch" remarks were unbecoming of his office.

"I think that it's always appropriate for the president of the United States to defend our flag, to defend the national anthem, and to defend the men and women who fought and died to defend it," spokeswoman Sarah Huckabee Sanders said.

"The president is not talking about race," she claimed.

TRT World's Giles Gibson reports more from Washington:

Courting controversy

Trump has wholeheartedly embraced the controversy, with his advisers suggesting it plays well with his largely-white base.

Trump also changed his Twitter background photo to an American flag.

All this has led critics to accuse Trump of creating a diversion from a serious of failures.

His efforts to repeal Barack Obama's health care reforms have run aground and would-be signature tax reforms are giving way to much less ambitious tax cuts.

At the same time, Trump faces a number of challenges from overseas, not least a war of words with North Korea that threatens to become a shooting war.

Trump has also faced criticism for his low-profile White House response to Hurricane Maria, which has left much of the US island territory of Puerto Rico.