President Trump told a gathering of military leaders Tuesday they should use American cities as “training grounds” and described a federal crackdown on crime in major cities as necessary due to “a war from within.”

Trump addressed dozens of top generals and admirals in Quantico, Va., where he said defending the homeland was the military’s “most important priority.” He signaled the leaders in the room could be tasked with aiding in federal interventions in Democratic-led cities such as Chicago and New York City.

“They’re very unsafe places, and we’re going to straighten them out one by one,” Trump said. “And this is going to be a major part for some of the people in this room. That’s a war, too. It’s a war from within.”

“I told [Defense Secretary Pete Hegseth], we should use some of these dangerous cities as training grounds for our military — National Guard, but our military, because we’re going into Chicago very soon,” Trump added. “That’s a big city with an incompetent governor.”

The White House has already directed the deployment of National Guard troops across Washington, D.C., and Memphis, Tenn., as part of an effort to quell crime in those cities. This week, announced he would send troops to Portland, Ore.

Trump has for weeks threatened to deploy the National Guard to other cities such as Chicago, New York and New Orleans, despite state and local officials pushing back and saying such a move would inflame tensions.

Democratic leaders have likened Trump’s use of the military in American cities to an authoritarian tactic.

“America is under invasion from within. We’re under invasion from within,” Trump said Tuesday. “No different than a foreign enemy, but more difficult in many ways because they don’t wear uniforms.”