US President Donald Trump criticised protests by NFL players for a second straight day and rescinded NBA star Stephen Curry's White House invitation in a series of tweets that outraged football and basketball stars and even prompted LeBron James to call the president a "bum."

Trump started by announcing that Curry, the immensely popular two-time MVP for the Golden State Warriors, would not be welcome at the White House for the commemorative visit traditionally made by championship teams.

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! — LeBron James (@KingJames) September 23, 2017

"Going to the White House is considered a great honor for a championship team. Stephen Curry is hesitating, therefore invitation is withdrawn!" Trump tweeted.

Later, Trump reiterated what he said at a rally in Alabama the previous night that NFL players who kneel for the national anthem should be fired, prompting immediate condemnation from a handful of team executives, the league commissioner and its players' union.

The Warriors said it was made clear to them that they were not welcome at the White House.

Roger Goodell of NFL just put out a statement trying to justify the total disrespect certain players show to our country.Tell them to stand! — Donald J. Trump (@realDonaldTrump) September 23, 2017

They said that when they go to Washington this season they will instead "celebrate equality, diversity and inclusion - the values that we embrace as an organisation."

Curry had said he did not want to go to the White House anyway, but the Warriors had not made a collective decision before Saturday.

"U bum (at)StephenCurry30 already said he ain't going!" James tweeted in a clear message to the president - a post that Twitter officials said was quickly shared many more times than any other he's sent.

"So therefore ain't no invite. Going to White House was a great honor until you showed up!"

Going to the White House is considered a great honor for a championship team.Stephen Curry is hesitating,therefore invitation is withdrawn! — Donald J. Trump (@realDonaldTrump) September 23, 2017

James also released a video on Saturday, saying Trump has tried to divide the country.

"He's now using sports as the platform to try to divide us," James said.

"We all know how much sports brings us together. ... It's not something I can be quiet about."

Warriors general manager Bob Myers said he was surprised by the invitation being pulled while Golden State coach Steve Kerr, after his team's first practice of the season said: "These are not normal times."