The quarter-back has refused to stand for the US national anthem on two occasions
Police officers in the US have threatened to boycott the home games of NFL team San Francisco 49ers if the franchise does not take action against Colin Kaepernick US anthem protest.
The quarter-back has refused to stand for the US national anthem on two occasions in protest at the shootings of African Americans by law enforcement and racial oppression.
The 49ers have backed Kaepernick's right to protest, while reaction has been divided in US society and among military veterans.
But NBC Bay Area has obtained a letter from Santa Clara Police Union, saying that that their members may not work at 49ers home games.
They also quote president of the Santa Clara Police Officers Association Frank Saunders as saying: "I'm already hearing it this week that next week on Monday Night Football, some officers are not going to work."
He is also quoted as saying that "The 49ers are allowing this to come out from an employee and it's making for a hostile work environment for us at the stadium."