US Senator Ted Cruz has accused the head of America's broadcast regulator of acting like a mafioso in the suspension of late-night host Jimmy Kimmel - the sharpest attack yet from a conservative Republican on the controversy.

He said Federal Communications Commission (FCC) chairman Brendan Carr's threat to ABC over their comedian's monologue about slain conservative influencer Charlie Kirk was dangerous as hell.

That's right out of Goodfellas, the Texas Republican said, as he affected a mobster's accent.

Other Republicans in Congress have been more muted in their criticism of how the FCC pressed Disney-owned ABC to take action on Kimmel, who was indefinitely suspended on Wednesday.

The row started after Kimmel appeared to suggest in his monologue on Monday night that the alleged gunman charged with murdering Kirk was a Maga Republican, although authorities in Utah have said the suspect was indoctrinated with leftist ideology.

Before ABC's decision, Carr said there would be consequences if Kimmel stayed on air. The FCC chairman said that Kimmel was appearing to directly mislead the American public in his on-air remarks.

The FCC is in charge of granting broadcast licenses to networks such as ABC, NBC and CBS, and they are required under statute to be in the public interest.

On his podcast Verdict with Ted Cruz, the senator emphasised on Friday that he hated what Kimmel said about Kirk, and he is thrilled that he was fired. He also said Carr was a good guy.

But what he [Carr] said there is dangerous as hell, Cruz added. And so he threatens, explicitly, we're going to cancel ABC's licence.

He warns that if the government gets into the business of bans and regulating what the media says that will end up bad for conservatives.

In the Oval Office, President Donald Trump defended Carr and said I disagree with Ted Cruz, who is ordinarily one of his staunchest allies. Another Republican Senator, Thom Tillis, told reporters that Cruz was absolutely right in his criticism of Carr, calling the chairman's comments unacceptable behaviour.

As this controversy unfolds, the implications for media freedom and the future of late-night television remain at stake.