President Donald Trump renews attack on NFL protesters

President Donald Trump has renewed his attack on NFL players who knelt during the national anthem, calling for them to be suspended without pay.

The US president, who triggered an uproar last year after condemning players who protested against social injustice, lashed out again after two Miami Dolphins players 'took a knee' during a pre-season game on Thursday.

"The NFL players are at it again - taking a knee when they should be standing proudly for the National Anthem," Trump wrote on Twitter.

"A football game, that fans are paying soooo much money to watch and enjoy, is no place to protest. Most of that money goes to the players anyway.

"Find another way to protest. Stand proudly for your National Anthem or be Suspended Without Pay!"

Trump's salvo came after Miami players Kenny Stills and Albert Wilson took a knee during a rendition of "The Star-Spangled Banner" on Thursday.

In a separate protest, Philadelphia Eagles players Malcolm Jenkins and De'Vante Bausby raised their fists during the playing of the song before their game against Pittsburgh Steelers.

Former San Francisco 49ers quarterback Colin Kaepernick started the protest when he declined to stand for the national anthem following the deaths of several unarmed black men during confrontations with law enforcement.

The protests had largely fizzled out until Trump last year described Kaepernick and other players who took a knee during the anthem as "sons of bitches" who should be fired.

Political analysts have predicted Trump would seek to keep the issue alive to energise supporters ahead of November's crucial mid-term elections, framing protesters as unpatriotic and disrespectful to the military.