President Donald Trump isn’t backing down after an online uproar over his comments that athletes should be fired for sitting out the national anthem.

“If a player wants the privilege of making millions of dollars in the NFL, or other leagues, he or she should not be allowed to disrespect our Great American Flag (or Country) and should stand for the National Anthem. If not, YOU’RE FIRED. Find something else to do!” Trump tweeted on Saturday, invoking his famous “Apprentice” catchphrase.

If a player wants the privilege of making millions of dollars in the NFL,or other leagues, he or she should not be allowed to disrespect…. — Donald J. Trump (@realDonaldTrump) September 23, 2017

…our Great American Flag (or Country) and should stand for the National Anthem. If not, YOU'RE FIRED. Find something else to do! — Donald J. Trump (@realDonaldTrump) September 23, 2017

NFL players attacked the president earlier in the day for his initial comments on Friday night. “Wouldn’t you love to see one of these NFL owners, when somebody disrespects our flag, to say: ‘Get that son of a bitch off the field right now, out. He’s fired. He’s fired!'” Trump told the crowd at a rally for Republican Alabama Senate candidate Luther Strange.

The National Football League denounced the remarks, with commissioner Roger Goodell calling them “divisive” and disrespectful.

“The NFL and our players are at our best when we help create a sense of unity in our country and our culture,” Goodell said in a statement on Saturday. “There is no better example than the amazing response from our clubs and players to the terrible natural disasters we’ve experienced over the last month. Divisive comments like these demonstrate an unfortunate lack of respect for the NFL, our great game, and all of our players, and a failure to understand the overwhelming force for good our clubs and players represent in our communities.”

New NFL statement pic.twitter.com/XHPgVvPPfH — Brian McCarthy (@NFLprguy) September 23, 2017

The players’ union also criticized Trump’s call to NFL owners to boot players who kneel or sit during the national anthem.

“We will never back down. We no longer can afford to stick to sports,” DeMaurice Smith, executive director of the NFL Players Association, tweeted.

We will never back down. We no longer can afford to stick to sports. pic.twitter.com/Ec3Bc4qt9h — DeMaurice Smith (@DeSmithNFLPA) September 23, 2017

Meanwhile, players bashed the president on social media.

“The behavior of the President is unacceptable and needs to be addressed. If you do not Condemn this divisive Rhetoric you are Condoning it!!” tweeted Richard Sherman of the Seattle Seahawks.

The behavior of the President is unacceptable and needs to be addressed. If you do not Condemn this divisive Rhetoric you are Condoning it!! — Richard Sherman (@RSherman_25) September 23, 2017

“It’s really sad man … our president is a asshole,” said LeSean McCoy of the Buffalo Bills.

It's really sad man … our president is a asshole — Lesean McCoy (@CutonDime25) September 23, 2017

“Does anyone tell trump to stick to politics, like they tell us to stick to sports? Smh,” wrote Eric Ebron of the Detroit Lions.

Does anyone tell trump to stick to politics, like they tell us to stick to sports? Smh. — Eric Ebron (@Ebron85) September 23, 2017

“Trump stay in ur place… football have nothing to do wit u smh,” said Zach Brown of the Washington Redskins.

Trump stay in ur place… football have nothing to do wit u smh — Zach Brown (@ZachBrown_55) September 23, 2017

Free agent quarterback Colin Kaepernick was among the first to protest the national anthem. “#Kaepernick we riding with you bro,” former NFL player Reggie Bush tweeted.

Trump is also at war with another sports league: The NBA. This year’s NBA champs, the Golden State Warriors, annouced on Saturday that they will officially skip the traditional White House visit following Trump’s criticism of star player Steph Curry.

“President Trump has made it clear we’re not invited,” the team said in a statement.

Trump slammed Curry earlier in the day over his remarks that he didn’t want to visit the White House amid growing racial tension. LeBron James, Kobe Bryant, and Chris Paul were among the NBA stars who came to his defense.