California's governor says will sue Donald Trump's administration after the National Guard was deployed to clamp down on protests in Los Angeles at the weekend.
Gavin Newsom, a Democrat, said the order to send in troops was illegal, and state Attorney-General Rob Bonta said his office was suing the federal government over its deployment of National Guard troops.
Reuters could not immediately confirm that a lawsuit had been filed.
It came as Mr Donald Trump expressed support for Mr Newsom's arrest.
At the weekend, Mr Newsom dared Tom Homan, the director of the Immigration and Customs Enforcement (ICE), to arrest him.
It came after Mr 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," Mr Trump said when asked if his border tsar should arrest the governor.
Mr Newsom called the president's response "an unmistakeable step toward authoritarianism".
"The President of the United States just called for the arrest of a sitting Governor," he posted on X.
"This is a day I hoped I would never see in America. I don’t care if you’re a Democrat or a Republican this is a line we cannot cross as a nation."
Following his support for Mr Newsom's arrest, Mr Trump said he would deploy additional National Guard troops to California if necessary.
Officials have also told Reuters the US military would deploy about 700 marines to Los Angeles until the National Guard troops arrived.
LA braces for fourth wave of protests
Sunday, local time, marked a third day of demonstrations against the administration's immigration raids, as protesters set fire to self-driving cars, blocked motorways and threw chunks of concrete and electric scooters at police officers, while police responded with tear gas and rubber bullets.
About a dozen National Guard members, along with Department of Homeland Security personnel, pushed back a group of demonstrators outside a federal building in downtown LA, video showed.
The city was braced on Monday for a fourth wave of protests.
"This is exactly what Donald Trump wanted," Mr Newsom said, in a post on X.
"He [Mr Trump] flamed the fires and illegally acted to federalise the National Guard. The order he signed doesn’t just apply to CA. It will allow him to go into ANY STATE and do the same thing.
Mr Trump hit back in a post on Truth Social, saying he made a "great decision" to send in the National Guard, as he accused Mr Newsom of being "incompetent".
"We made a great decision in sending the National Guard to deal with the violent, instigated riots in California. If we had not done so, Los Angeles would have been completely obliterated," said Mr Trump.
Later, he blamed "insurrectionists" for the unrest.
"The people that are causing the problems are professional agitators and insurrectionists," Mr Trump told reporters at the White House.
"They're bad people, they should be in jail," he added.
Despite Mr Trump's language, he has not invoked the Insurrection Act, an 1807 law that empowers a president to deploy the US military to suppress events such as civil disorder.
He did not reply when asked several times by reporters whether he planned to invoke the act, nor give evidence as to why the street protesters were referred to by him as "insurrectionists".
He went on to lash out again at Mr Newsom, who has been widely tipped as a possible 2028 presidential candidate, over the unrest.
"He's done a terrible job. Look, I like Gavin Newsom, he's a nice guy — but he's grossly incompetent, everybody knows," Mr Trump said.
'Dangerous escalation'
Meanwhile, the mayor blamed the Trump administration for inciting tension by sending in the National Guard. She also condemned protesters after some burned cars and hurled bottles at police
"We do not want to play into the [Trump] administration’s hands," Ms Bass said, adding the administration’s actions in LA had “caused fear and panic”.
"What we’re seeing in Los Angeles is chaos provoked by the administration. Deploying federalised troops is a dangerous escalation."
On Monday, the US Northern Command said 300 members of the California National Guard had been deployed to three spots in the Los Angeles area.
Homeland Security Secretary Kristi Noem told CBS program Face the Nation that the National Guard would provide safety around buildings to people engaged in peaceful protest and to law enforcement.
The unrest in LA has become a flashpoint in Mr Trump's signature effort to clamp down on illegal immigration.
The Republican president has pledged to deport record numbers of people who are in the country illegally and to lock down the US-Mexico border, setting the ICE border enforcement agency a daily goal of arresting at least 3,000 migrants.
The Trump administration's immigration enforcement measures have also included residents who are in the country legally, some with permanent residence, spurring legal challenges.
Defense Secretary Pete Hegseth said on Saturday the Pentagon was prepared to mobilise active-duty troops "if violence continues" in LA, and Marines at nearby Camp Pendleton were on high alert.
Vanessa Cardenas, the head of the immigration advocacy group America's Voice, accused the Trump administration of "trumping up an excuse to abuse power, and deliberately stoke and force confrontations around immigration".
Mexican President Claudia Sheinbaum on Monday condemned violent acts committed during the protests.
Ms Sheinbaum, speaking at her morning press conference, also called on US authorities to respect the rule of law in migration processes.
"It must be clear: We condemn violence wherever it comes from," she said.
"We call on the Mexican community to act peacefully and not fall for provocations."
She did not specifically call for an end to the protests.
ABC/Reuters
