Members of the Detroit Lions take a knee during the playing of the national anthem prior to the start of the game against the Atlanta Falcons at Ford Field on September 24, 2017 in Detroit, Michigan.

President Donald Trump on Tuesday called for changes to U.S. tax law affecting the National Football League, fueling a feud with the league and its players over protests that he says disrespect the nation.

"Why is the NFL getting massive tax breaks while at the same time disrespecting our Anthem, Flag and Country? Change tax law!" Trump wrote in a post on Twitter.

Donald Trump tweet