US President Donald Trump on Sunday once again lambasted US professional football players who insult or disrespect the flag and the national anthem as a sign of protest, stating that they should be fired or suspended.

“If NFL (National Football League) fans refuse to go to games until players stop disrespecting our Flag and Country, you will see change take place fast. Fire or suspend!” Trump wrote on his Twitter account.

“…NFL attendance and ratings are WAY DOWN. Boring games yes, but many stay away because they love our country. League should back US,” Trump added the in another tweet.

The controversy erupted last Friday when Trump at an Alabama rally criticised NFL players who have engaged in protests during the playing of the national anthem prior to their games, Efe reported.

Last year, African American Colin Kaepernick — who, at the time, was playing for the San Francisco 49ers — attracted attention for not rising to his feet during the national anthem.

Kaepernick had said at the time that he was not going to stand during the playing of the anthem because he felt that the US oppresses blacks and other people of colour.

“Wouldn’t you love to see one of these NFL owners, when somebody disrespects our flag, you’d say, ‘Get that son of a bitch off the field right now. Out! He’s fired,'” Trump said — to loud applause — at the rally in Huntsville, Alabama.

Trump also got involved in another brouhaha on Saturday when he withdrew an invitation for Golden State Warriors NBA player Stephen Curry to visit the White House.

Curry had admitted that he would vote against his team visiting the White House, as is traditional, to celebrate the NBA title they won last season, adding that his decision came in protest against the president.

After Trump’s broadside, the team confirmed that it will not visit the White House and said that it will use its visit to Washington next February to celebrate “equality, diversity and inclusion.”

Curry received messages of support from other NBA stars including Lebron James, with the Cleveland Cavaliers, the team that lost the final to Golden State last season.

On his Twitter account, James called Trump a “bum” and blasted the president by saying “Going to White House was a great honour until you showed up!”