Chicago police will not collaborate with any National Guard troops or federal agents if US President Donald Trump deploys them to the city in the coming days as threatened, Mayor Brandon Johnson said on Saturday.

The Democratic mayor, surrounded by other city leaders, signed an executive order aimed at preparing Chicago for any US enforcement operation, as Trump has done in Los Angeles and Washington, and urged the Republican president to reverse course.

“This is about making sure that we are prepared,” he told reporters as he signed the order, adding that the order aimed to offer “real, clear guidance” to city government workers and “all the Chicagoans of how we can stand up against this tyranny”.

The executive order says that Chicago police officers will continue to enforce state and local laws but will not assist with any patrols, arrests or other law enforcement actions alongside federal officers, including the National Guard.

It also directs city police to wear their official police uniforms, continue to identify themselves, follow body camera procedures and not to wear masks to clearly distinguish themselves from any federal operations, according to a copy of the order.

“The deployment of federal military forces in Chicago without the consent of local authorities undermines democratic norms, violates the City’s sovereignty, threatens civil liberties, and risks escalating violence rather than securing the peace,” the order says.

Trump has been threatening to expand his federal crackdown on Democrat-led US cities to Chicago, casting the use of presidential power as an urgent effort to tackle crime even as city officials cite declines in homicides, gun violence and burglaries.

Local officials and residents in Chicago, the nation’s third-largest city, have been preparing for the possible arrival of federal agents and troops, and Johnson said they have received credible reports that action could come within days.

The White House dismissed Johnson’s move and accused Democrats of trying to make tackling crime a partisan issue.

“If these Democrats focused on fixing crime in their own cities instead of doing publicity stunts to criticise the President, their communities would be much safer,” White House spokeswoman Abigail Jackson said in a statement.

While it is unclear how much state and local officials can do to push back against any US deployment, the mayor said he was pursuing any legal and legislative measures available, including possible lawsuits.

“We will use the courts if that’s necessary,” Johnson said.

Trump, meanwhile, has repeatedly said he wants to be asked for federal agents to be deployed to various cities, even as he continues to threaten to send them anyway without any formal request.

Illinois Governor J.B. Pritzker, a Democrat whose name has also been floated as a possible 2028 presidential candidate, has said the president lacks the legal authority to deploy troops to his state if not requested by the governor.

That differs from Washington, a federal city whose police department Trump took over.Previous deployments of the National Guard to Chicago were coordinated with local officials.

A president’s power to send in troops is limited under US law, but there are no restrictions on the deployment of federal law enforcement officers, such as ICE agents.