The National Football League (NFL) and its players' union have denounced US President Donald Trump for suggesting that club owners fire players who kneel during the national anthem.
Trump, during a political rally in Alabama on Friday night, said American football players who refuse to stand during "The Star-Spangled Banner" are disrespecting the American flag and deserve to lose their jobs.
Several athletes, including a handful of NFL players, have in recent months refused to stand during the anthem as a silent protest against racial injustice.
Quarterback Colin Kaepernick, who started the trend last year when he played for the San Francisco 49ers, has not been signed by an NFL team for this season.
"That's a total disrespect of our heritage," said Trump, referring to the protesting players. "That's a total disrespect of everything that we stand for."
Trump went on to say: "Wouldn't you love to see one of these NFL owners, when somebody disrespects our flag, you'd say, 'Get that son of a b**** off the field right now. Out! He's fired'."
Several sports personalities, commentators and social media users interpreted Trump's "son of a b****" as a thinly veiled attack on Kaepernick.
Roger Goodell, the NFL commissioner, fired back at the US president in a statement on Saturday.
"Divisive comments like these demonstrate an unfortunate lack of respect for the NFL, our great game and all of our players," Goodell said.
DeMaurice Smith, executive director of the NFL Players Association (NFLPA) also released a statement saying that "no man or woman should ever have to choose a job that forces them to surrender their rights."
Smith added: "The line that marks the balance between the rights of every citizen in our great country gets crossed when someone is told to just 'shut up and play'."
Responding to the president, Kaepernick's mother, Teresa, took aim at Trump's remarks in a tweet.
"Guess that makes me a proud bitch!" she tweeted, replying to a journalist who shared the story.
Teresa Kaepernick's tweet has been shared more than 46,000 times.
Famous American sports personalities and social media users also voiced their support for the protesting athletes by using the hashtag #TakeAKnee on Twitter.
Travis Waldron, a sport and politics reporter for the Huffington Post, said that the president has based his support around people who believe that black athletes and black people generally need to "stay in their place and not speak out".
Speaking to Al Jazeera from Washington, DC, Waldron said: "Trump sees these black athletes as kind of an avatar for this movement for racial justice that has been going on in this country. He fundamentally does not see the racial injustice of this country as a problem of our heritage."
Trump also claimed the anthem protest was the top reason NFL viewership had waned.
"You know what's hurting the game? When people like yourselves turn on television and you see those people taking the knee when they're playing our great national anthem," he said.
Trump encouraged his supporters to leave the stadium next time they spot a player failing to stand.
The US president once owned the New Jersey Generals of the US Football League, the franchise that tried to challenge the NFL in the 80s by playing in the spring.
The NFL season each year kicks off around September.
LeBron James calls Trump 'a bum'
Protesting football players were not the only professional athletes targeted by Trump in recent days.
In an early morning Twitter message on Saturday, the president rescinded a White House invitation to basketball star Stephen Curry, who had said he would "vote" against the planned visit by the National Basketball Association (NBA) champion Golden State Warriors.
"Going to the White House is considered a great honor for a championship team. Stephen Curry is hesitating, therefore invitation is withdrawn!" Trump tweeted.
The Golden State Warriors announced their decision not to visit the White House in February in a statement on Saturday.
"While we intended to meet as a team at the first opportunity we had this morning to collaboratively discuss a potential visit to the White House, we accept that President Trump has made it clear that we are not invited," the team said.
Three-time NBA champion and Cleveland Cavaliers forward LeBron James came to Curry's defence on Saturday, disputing Trump's assertion that visiting the White House was an honour.
"U bum @StephenCurry30 already said he ain't going! So therefore ain't no invite. Going to White House was a great honor until you showed up!" James, a prominent supporter of Hillary Clinton during the 2016 presidential elections, said on Twitter.