President Donald Trump and his administration officials warned that the use of the military in response to protests against his immigration crackdown may not be limited to just Los Angeles, saying it could be the first "of many" -- and that protesters could be met with "equal or greater force."

Trump told reporters in the Oval Office on Tuesday that his administration was going to enforce its deportation policy strictly and that it would not tolerate violent protests against ICE officers.

"This is the first, perhaps, of many," Trump said of the deployment of 4,000 National Guardsmen and 700 Marines to Los Angeles as demonstrators clash with law enforcement amid the protests.

Demonstrators have clashed with law enforcement sporadically for days, and Trump called in the National Guard, against Gov. Gavin Newsom's wishes, in an attempt to quell the violence and allow immigration enforcement to continue.

"You know, if we didn't attack this one very strongly, you'd have them all over the country, but I can inform the rest of the country, that when they do it, if they do it, they're going to be met with equal or greater force," Trump continued.

The president's threats come as California's leaders and 22 Democratic governors decry Trump's show of force as a breach of the state's sovereignty and a provocative escalation.

Trump's words were echoed in testimony given by Defense Secretary Pete Hegseth during a congressional hearing on Capitol Hill earlier in the day.

"So in Los Angeles, we believe that ICE, which is a federal law enforcement agency, has the right to safely conduct operations in any state, in any jurisdiction in the country," Hegseth said. "ICE agents should be allowed to be safe and doing their operations, and we have deployed National Guard and the Marines to protect them in the execution of their duties, because we ought to be able to enforce ... immigration law in this country."

The president suggested he is open to invoking the Insurrection Act in response to the protests. The act authorizes the president to deploy military forces inside the United States to suppress rebellion or violence.

The National Guard and Marines, under Trump's current authorization, are not allowed to act in a law enforcement capacity because of the 1878 Posse Comitatus Act.

"There were areas of Los Angeles last night where you could call it an insurrection," Trump said.

Trump repeated claims, without evidence, that the protesters are "paid insurrectionists." He decried some protesters who were damaging streets and targeting members of the National Guard.

Despite claims from Trump that there were fires and "bad scenes" on Monday night, there wasn't anything all that violent. ABC News observed police moved protesters using skirmish lines and less lethal rounds around the city for a few hours, but there was no widespread violence compared to the weekend.

And although Trump claimed that Los Angeles was "under siege," the incidents had been confined on Sunday and Monday to a relatively small area of downtown Los Angeles -- about a 10-block area.

So far, the National Guard's presence and role in handling the protests appears to have been minimal.

ABC News observed National Guard troops standing outside of a federal building and the Los Angeles Police Department and other local agencies clearing the streets and interacting with protesters.

The administration has not immediately provided details about the guardsman's actions from Monday.

Congressional Republicans -- including House Speaker Mike Johnson and Senate Majority Leader John Thune -- backed the president's use of the military in the situation.

"Clearly, the local officials there, for whatever reason, didn't seem up to the task of getting the job done there," Thune told reporters Tuesday.

Although Senate Minority Leader Chuck Schumer said "violence in the riots is outrageous," he called Trump's order to send in troops "provocative" and "dangerous."

"It really threatens the bedrock of our democracy," the New York Democrat said.

Trump said the National Guard will be in the Los Angeles area "until there's no danger," declining to put a timetable on ending the deployment.

"It's easy. Look, it's common sense. … When there's no danger, they'll leave," he said.

ABC News' Alex Stone, Lalee Ibssa, Isabella Murray and Kelsey Walsh and contributed to this report.