Colin Kaepernick and teammate Eric Reid (35) kneel during the playing of the US national anthem. Photo: Kirby Lee/Reuters

WASHINGTON – US President Donald Trump on Friday invited National Football League players who protest social injustice by kneeling during the national anthem - a gesture he has criticized - to suggest prisoners for potential pardons.

“I'm going to ask them to recommend to me people that were unfairly treated - friends of theirs or people that they know about - and I'm going to take a look at those applications,” Trump told reporters before heading to Canada for the G7 summit.

“And if I find, and my committee finds that they are unfairly treated, then we will pardon them or at least let them out.”

Trump has recently wielded his presidential powers to pardon a variety of people, from late heavyweight champion boxer Jack Johnson to conservative firebrand Dinesh D'Souza.

The US president has relentlessly criticized mostly black NFL players who have taken a knee during “The Star-Spangled Banner” in protest at racial and social injustice.

The protests were launched by former San Francisco 49ers quarterback Colin Kaepernick in 2016 following the deaths of several unarmed black men during confrontations with law enforcement.

Trump triggered a wave of protests across the NFL last season after describing protesting players as “sons of bitches” who should be fired.

Read: Trump invites NHL champs Capitals to White House but not NBA winners

The NFL last month changed its policy over the national anthem, ruling that players on the field must stand or face fines, but players would have the option of remaining in the locker room during the pre-match ritual.

Trump, who this week scrapped a planned visit to the White House by the Super Bowl champion Philadelphia Eagles after only a handful of players said they would visit, again reiterated his belief Friday that players should stand for the anthem.

“You have a lot of people in the NFL, in particular, but in sports leagues. They're not proud enough to stand for our national anthem,” he said. “I don't like that.

“We have a great country, you should stand for our national anthem. You shouldn't go in a locker room when our national anthem is played.”

Agence France-Presse (AFP)