President Trump extended his attack on NFL players who kneel during the national anthem in a series of tweets throughout the day Sunday, suggesting fans boycott games as he continued his call for team owners to "fire or suspend" the offenders.

He tweeted Sunday afternoon: "Sports fans should never condone players that do not stand proud for their National Anthem or their Country. NFL should change policy!"

Earlier, he wrote, "If NFL fans refuse to go to games until players stop disrespecting our Flag & Country, you will see change take place fast. Fire or suspend!"

He followed that with this tweet: "...NFL attendance and ratings are WAY DOWN. Boring games yes, but many stay away because they love our country. League should back U.S."

The president also retweeted a supporter who posted a graphic calling for a "BOYCOTT!!" of the NFL.

Trump started his criticism in earnest Friday night when he asked a crowd at a political rally in Alabama: "Wouldn't you love to see one of these NFL owners, when somebody disrespects our flag, to say 'get that son of a b ---- off the field right now? Out! He's fired! He's fired.'"

He continued the criticism Saturday when he rescinded Golden State Warrior Stephen Curry’s invitation to the White House this spring to honor his team’s 2017 NBA championship.

Quarterback Colin Kaepernick started the 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.

Trump’s weekend remarks were met with sharp criticism from professional athletes and team owners — including NFL Commissioner Roger Goodell, who called the remarks “divisive,” and NBA star LeBron James, who called Trump a “bum.”

"The NFL and our players are at our best when we help create a sense of unity in our country and our culture. 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," Goodell said. "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."

At least seven team owners donated $1 million each to Trump's inaugural committee.

Los Angeles Chargers owner Dean Spanos, Atlanta Falcons owner Arthur Blank, New York Giants owners John Mara and Steve Tisch, Miami Dolphins owner Stephen Ross, Indianapolis Colts owner Jim Irsay, Tennessee Titans' controlling owner Amy Adams Strunk and San Francisco 49ers owner Jed York were among the league powerbrokers who issued condemning statements through their clubs.

"The callous and offensive comments made by the president are contradictory to what this great country stands for," York said. "Our players have exercised their rights as United States citizens in order to spark conversation and action to address social injustice. We will continue to support them in their peaceful pursuit of positive change in our country and around the world."

Added Green Bay Packers President and CEO Mark Murphy: "We believe it is important to support any of our players who choose to peacefully express themselves with the hope of change for good. As Americans, we are fortunate to be able to speak openly and freely."

"I know our players who kneeled for the anthem, and these are smart young men of character who want to make our world a better place for everyone," Ross, owner of the Dolphins, said. "They wanted to start a conversation and are making a difference in our community, including working with law enforcement to bring people together. We all can benefit from learning, listening and respecting each other."

The Associated Press contributed to this report.