The mayors of New York City and Chicago say they will take President Donald Trump to court if he sends unidentified US government agents to police their cities.
But Chicago Mayor Lori Lightfoot also said she would accept an influx of FBI agents and other identified law enforcement officials from the Trump administration, an acknowledgement of the scale of gun violence and other crimes plaguing her city.
Lightfoot and New York City Mayor Bill de Blasio spoke a day after Trump said he would send law enforcement to several cities including Baltimore, Chicago, New York and Philadelphia to crack down on protests against racism and police brutality ignited by George Floyd's death in Minneapolis police custody on May 25.
A Republican, Trump made a point of saying the mayors of the cities on his list were liberal Democrats, underpinning concerns the threat was politically motivated.
Federal agents last week were dispatched to counter protests in Portland, Oregon, where protesters have complained of agents making arrests without identifying themselves and using unmarked rental cars.
Opinion polls show Trump trails Democratic challenger Joe Biden in the run-up to a November 3 presidential election. Trump has sought to make a crackdown a campaign issue, taking the spotlight off his response to the coronavirus pandemic, a weak point for him in the polls.
De Blasio said Trump's threat was likely bluster, but added he would challenge any deployment in the courts. He said the actions of unidentified officers grabbing citizens in Portland "appeared to violate basic constitutional rights."
Lightfoot said she had been told that no unidentified officers would be deployed in Chicago.
The Chicago Tribune had reported that the US Department of Homeland Security (DHS), would deploy 150 agents to help tamp down violence in the city.
ILightfoot said reinforcements would come from the FBI, the Drug Enforcement Administration and the Bureau of Alcohol, Tobacco, Firearms and Explosives and "plug into" federal agencies already coordinating with the city on crime.
The Portland protests have gone on for more than 50 nights.
On Monday, video showed federal agents firing tear gas, protesters pulling down fencing around the federal courthouse, and hundreds of people dressed in yellow who said they were mothers and fathers demanding the agents withdraw.
DHS has placed about 2000 officials from US Customs and Border Protection (CBP) and other agencies on standby for possible deployment to cities, the New York Times reported.
A CBP official told Reuters that officers from three border units in paramilitary-type operations had been deployed to Portland.
White House spokeswoman Kayleigh McEnany told a briefing on Tuesday that dispatching agents was justified by a federal statute empowering the secretary of Homeland Security to deputise agents to protect federal property and people on that property.
At a separate briefing, acting Homeland Security secretary Chad Wolf said his agents were properly identifying themselves in Portland.
"We are only targeting and arresting those who have been identified as committing crime," Wolf said.
However, legal experts said there were limits to Trump's power and that he could be challenged in court.
"The president is not the king," said Kent Greenfield, a Boston College law professor.