The Mayor of New York has said he would go to court to stop US President Donald Trump from sending federal troops to the city to quell rising crime.
Mr Trump has threatened to send more federal law enforcement into US cities to quell anti-racism protests, a move he called necessary security action.
However, his critics have labelled the threat an election year political stunt.
After the Department of Homeland Security deployed scores of Border Patrol police and federal marshals, many in combat fatigues, to Portland, Oregon, last week, Mr Trump said he could do so in other Democrat-led cities.
After the DHS force arrived, video showed them taking some demonstrators away in unmarked vehicles.
Most have been freed, but critics, including Oregon's governor and senators, likened it to "secret police" in more repressive societies.
"This president blusters and bluffs and says he's gonna do things and they never materialize on a regular basis," New York Mayor Bill de Blasio told reporters.
"If he tried to do it, it would only create more problems, it would backfire, wouldn't make us safer and we would immediately take action in court to stop it.
"From my point of view, this would be yet another example of illegal and unconstitutional actions by the President," the mayor added.
Oregon has sued DHS for rights violations, while the state's governor, Kate Brown, demanded the officers be withdrawn, calling the deployment a political "photo op".
DHS officials yesterday said they have no intention of pulling back in Portland.
According to reports, DHS is preparing to send 150 paramilitary personnel to Chicago after police there clashed with demonstrators seeking to tear down a statue of Christopher Columbus.
Separately, 63 people were shot and 12 killed over the weekend in ongoing gun violence in the city, according to local media.
"We're looking at Chicago, too. We're looking at New York," Mr Trump told reporters.
"Look at what's going on. All run by Democrats, all run by very liberal Democrats, all run really by radical left. We can't let this happen to the city.
"I'm going to do something, that I can tell you, because we're not going to leave New York and Chicago and Philadelphia, Detroit and Baltimore," he said.
In a statement, DHS said it "does not comment on any allegedly leaked operations".
Mr Trump's decision to have federal law enforcement authorities intervene in local protests has sparked anger and legal questions.
Protests against racism and police brutality, have been taking place across the United States since a black man, George Floyd, was killed by a white Minneapolis police officer on 25 May.
Mr Trump has sought to paint the demonstrators as radical leftists intent on destroying the country.
Facing an uphill battle for re-election in November against Democrat Joe Biden, Mr Trump is using the protests to rally support from his conservative base, Democrats say.
Yesterday, the mayors of six major cities - Atlanta, Washington, Seattle, Chicago, Portland and Kansas City - said in a letter to Homeland Security Acting Secretary Chad Wolf and Attorney General Bill Barr that the uninvited paramilitary deployments violate the Constitution.
"Deployment of federal forces in the streets of our communities has not been requested nor is it acceptable," they wrote.
"It is concerning that federal law enforcement is being deployed for political purposes," they said.
Michigan state Attorney General Dana Nessel called the threat to send federal officers to Detroit a threat to peace and the right to protest.
"We are a nation of laws, and the President's attempts to intimidate our communities with threats of violence could not be more un-American," she said.
