US President Donald Trump said Monday it would be “great” if California governor Gavin Newsom was arrested, in an extraordinary threat as the two men sparred over protests in Los Angeles.

Republican Trump, 78, deployed the National Guard in America’s second city on Saturday after clashes erupted over immigration raids – but he did not seek the Democratic governor’s consent, the first time a US president has taken such an action in 60 years.

As temperatures rose, Newsom, 57, then dared Trump’s border czar Tom Homan over the weekend to arrest him, after Homan said the governor and LA mayor Karen Bass could face federal charges of trying to impede immigration agents.

“I would do it if I were Tom. I think it’s great,” Trump told reporters when asked if Homan should arrest Newsom, as the Republican president arrived on his Marine One helicopter at the White House.

“Gavin likes the publicity, but I think it would be a great thing.”

Trump said Newsom, who has been widely tipped as a possible 2028 presidential candidate, had “done a terrible job” in curbing the Los Angeles clashes.

“Look, I like Gavin Newsom, he’s a nice guy – but he’s grossly incompetent, everybody knows,” Trump said.

Trump later said that “I don’t want a civil war,” but that “civil war would happen if you left it to people like him.”

Newsom has bitterly accused Trump of manufacturing the crisis for political gain, saying that local law authorities could have handled the protests without the National Guard.

On Sunday, he blasted border chief Homan, telling MSNBC: “Come after me, arrest me, let’s just get it over with, tough guy.”

The Democrat then branded Trump as “dictatorial” later Monday after the Trump administration deployed 700 active-duty Marines to Los Angeles.