Sunday 24 September 2017 22:11, UK
The Pittsburgh Steelers, the Seattle Seahawks and Tennessee Titans all stayed in their locker rooms for the US national anthem during their games on Sunday.
Steelers players took the field within a few seconds of the anthem's end prior to their game against the Chicago Bears, with quarterback Ben Roethlisberger one of the first players out of the tunnel.
Pittsburgh's left tackle Alejandro Villanueva, a former Army Ranger who served three tours in Afghanistan before playing in the NFL, stood just outside the tunnel with his hand over his heart, a few yards ahead of his team-mates while the anthem was being played.
US president Donald Trump has referred to players who knelt in protest against racial injustice in the US as "sons of b******" and urged NFL owners to fire them.
On Sunday he took to Twitter urging fans to boycott NFL games if players continued to kneel.
His remarks appear to have galvanised players in their determination to protest with dozens of players electing to kneel across the NFL.
Steelers head coach Mike Tomlin is determined not to let the growing controversy divide Pittsburgh's locker room.
"These are very divisive times for our country," Tomlin told CBS. "For us, as a football team it is about us remaining solid. We are not going to be divided by anything said by anyone.
"This collection of men, we are chasing something here in 2017 and we are not going to play with football players and football coaches.
"We are not participating in the anthem today, not to be disrespectful to the anthem but to remove ourselves from the circumstance."
Later in the day both the Seahawks and the Titans followed suit prior to their game in Tennessee.
A statement on behalf of Seahawks players said: "As a team, we have decided we will not participate in the national anthem. We will not stand for the injustice that has plagued people of colour in this country.
"Out of love for our country and in honour of the sacrifices made on our behalf, we unite to oppose those that would deny our most basic freedoms. We remain committed in continuing to work towards equality and justice for all.
Quarterback Colin Kaepernick started the kneeling movement last year when he played for the San Francisco 49ers, refusing to stand during "The Star-Spangled Banner" to protest the treatment of black people by police. Kaepernick became a free agent and has not been signed by a new team for this season.
