World championship leader Lewis Hamilton on Thursday backed American sports stars who protest at racial injustice during their national anthem, a stance supported by Mexican driver Sergio Perez. 

The three-time Formula One world champion Hamilton has been vociferous on social media in supporting players in the NFL and other sports who have "taken the knee" during the national anthem.

"I really think I can identify with those individuals, hence the posts I put up," Hamilton told reporters at the Sepang International Circuit ahead of Sunday's Malaysian Grand Prix

"I think it's open for anyone to have freedom of speech," Mercedes driver Hamilton said. 

"I guess we all have a role to play to make a difference in the world. Particularly if your leader is not in that area, it takes for the people to stand together."

President Trump has been at loggerheads with NFL players, owners and league officials over the symbolic gesture intended to draw attention to racial injustice in the United States.

Trump escalated the row further last week when he called for owners to fire players that do not stand for the anthem.

Trump's remarks have brought a wave of protests in response.

Last weekend more than 150 NFL players took a defiant stance, kneeling, linking arms or raising clenched fists during the playing of the "Star-Spangled Banner" before games.

Force India's driver Perez also gave his support Thursday to the protesting sports stars.

"Being a sportsman gives you a lot of voice," Perez told reporters. 

"It is important, not only in the States, all around the world, to try to care about what is going on in the world, not only being focused on your job.

"You have some obligations you have to look after."