Quantico, Virginia - President Donald Trump said Tuesday that the US faces a "war from within" from crime and immigration, in a darkly authoritarian speech to a rare meeting of the top military officers.

Addressing generals and admirals summoned from around the world by Pentagon chief Pete Hegseth, Republican Trump warned that the military would be involved in his crackdowns on a number of Democratic-run cities.

"We're going to straighten them out one by one, 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," Trump said in front of a huge American flag in Quantico, Virginia.

Trump added that he had signed an order to set up a military quick reaction force to quell civil disturbances "because it's the enemy from within, and we have to handle it before it gets out of control."

Trump began his speech by talking about the US military in general terms, saying it was "reawakening the warrior spirit."

But much of the extraordinary, hour-long address had a highly political tone, in a break with tradition by previous presidents who have tended to avoid overt domestic politics when addressing troops.

As the audience of officers remained silent, Trump also lashed out at the media, calling them "sleazebags."

Former Fox News host-turned Defense Secretary Hegseth summoned the highly unusual gathering of hundreds of officers last week, before Trump then announced that he would also speak.

Striding the stage, the Pentagon chief said the military must fix "decades of decay" as he lashed out at so-called "woke" policies in the military.

The speeches by Trump and Hegseth come as the US military faces controversy both at home and abroad, with Trump deploying troops in Los Angeles and Washington, and shortly in Portland and Memphis.