US President Donald Trump said on Monday he would call a national emergency and federalise Washington, DC after Mayor Muriel Bowser said its police would not cooperate with Immigration and Customs Enforcement (ICE).
At issue is the provision of information on individuals living in, or entering, the United States illegally.
Trump's threat adds to a move critics have seen as federal overreach.
The comments come after several thousand protesters hit the streets this month over Trump's August deployment of National Guard troops in the capital to "re-establish law, order, and public safety," after calling crime a blight on the city.
"In just a few weeks. The "place" is absolutely booming... for the first time in decades, virtually NO CRIME," Trump said on Truth Social.
He blamed "Radical Left Democrats" for pressuring Bowser to inform the government about the non-cooperation with ICE.
The National Guard serves as a militia answering to the governors of the 50 states, except when called into federal service.
The DC National Guard reports directly to the president.
