Donald Trump has hit out at Nike over its Just Do It ad campaign featuring Colin Kaepernick.
The US president, a frequent critic of protesting NFL players, also said he now finds the sport “hard to watch”.
Kaepernick, a former quarterback with the San Francisco 49ers, was the first athlete to kneel during The Star-Spangled Banner to protest against police brutality against blacks.
“Nike is getting absolutely killed with anger and boycotts,” Mr Trump tweeted after the sportswear giant chose to feature Kaepernick in a new campaign.
“I wonder if they had any idea that it would be this way? As far as the NFL is concerned, I just find it hard to watch, and always will, until they stand for the FLAG!”
The new ad is scheduled to air during the NFL season opener on Thursday night as well as during the US Open tennis tournament and other major sporting events.
It highlights superstar athletes LeBron James, Serena Williams and others, and touches on the controversy of NFL players protesting racial inequality, police brutality and other issues by demonstrating during the national anthem.
The endorsement deal between Nike and Kaepernick prompted a flood of debate in the US after it was first revealed on Tuesday.
I stand with Nike, every day, all day.
It became a trending topic on Twitter and other social networks, with some fans urging a boycott of the company’s clothes and trainers — even burning and cutting out the signature swoosh logos on their gear.
“I stand for anybody that believes in change. I stand for anybody that believes in a positive attitude,” LeBron James said in support. “I stand with Nike, every day, all day.”
In the two-minute advert Kaepernick narrates before appearing halfway through.
As a camera pans to reveal his face, a reflection of a United States flag is visible on the facade of a building behind him.
Kaepernick says: “Believe in something, even if it means sacrificing everything.”
At the start of the ad, Kaepernick says: “If people say your dreams are crazy, if they laugh at what you think you can do, good. Stay that way, because what nonbelievers fail to understand is that calling a dream crazy is not an insult, it’s a compliment.”
The ad’s universal theme is about athletes pushing for bigger dreams. It features young athletes who compete amid various challenges, touching on issues of gender, disabilities and weight loss, among others.
Kaepernick says at the end: “Don’t ask if your dreams are crazy. Ask if they are crazy enough.”
The ad is also expected to air this week during college football and MLB games, and stream on various music, gaming and other platforms, Nike spokeswoman Sandra Carreon-John said.
Kaepernick, who has not played a game since 2016, has not spoken to the media publicly since opting out of his contract with San Francisco and becoming a free agent in 2017.
He scored a legal victory last week in his grievance against the NFL and its 32 teams when an arbitrator allowed his case to continue to trial.
The quarterback claims NFL team owners conspired to keep him out of the league because of his protests.
His case hinges on whether owners worked together rather than decided individually to not sign Kaepernick.
A similar grievance is still pending by former San Francisco teammate Eric Reid who joined in the protests.
Kaepernick already had a deal with Nike that was set to expire, but it was reportedly renegotiated into a multi-year agreement to make him one of the faces of Nike’s 30th anniversary Just Do It campaign.
The deal would put Kaepernick in the top bracket of NFL players with Nike.