Mayor Rahm Emanuel accused the Trump administration on Sunday of trying to blackmail Chicago and other sanctuary cities by threatening to withhold crime-fighting money if police departments don’t cooperate with federal immigration agents.

Emanuel, flanked by Chicago Police Supt. Eddie Johnson and U.S. Rep. Danny Davis, announced that Chicago will sue the Trump administration, claiming new requirements to receive federal money are unconstitutional.

The Justice Department fired back at Emanuel, pointing out the city’s growing problem with violent crimes.

“In 2016, more Chicagoans were murdered than in New York City and Los Angeles combined. So it’s especially tragic that the mayor is less concerned with that staggering figure than he is spending time and taxpayer money protecting criminal aliens and putting Chicago’s law enforcement at greater risk,” Justice Department spokeswoman Sarah Isgur Flores told the Sun-Times.

However, the two law firms handling the case for the city, Riley Safer and Wilmer Hale, are not charging for their services, the city said.

RELATED: Rahm to sue Justice Department over sanctuary cities fund cut threat

At issue is the Trump administration’s stepped up actions to force local governments shielding undocumented immigrants — such as Chicago and Cook County — to cooperate with federal immigration authorities who want access to local jails, information about undocumented immigrants and other accommodations.

The lawsuit will argue that President Donald Trump and Attorney General Jeff Sessions are acting unconstitutionally in threatening the city’s Edward Byrne Memorial Justice Assistance Grant program funds, meant to support local policing efforts. The suit will be filed Monday in federal court in Chicago.

Chicago has used the federal grants to buy SWAT equipment, police vehicles, radios and Tasers. Last year, the program gave Chicago $2.3 million.

Other cities and states on the Justice Department’s radar include California, New York City, New Orleans, Philadelphia, Las Vegas, Miami and Milwaukee. Emanuel said Chicago is the first city to file such a lawsuit, but he expects other cities to challenge the new requirements.

Federal officials published the application for Byrne grants on Thursday, with a deadline of Sept. 3. The application included the new conditions, which Emanuel said Trump and Sessions are using to “coerce” the city into choosing between its values and effective policing. He said immigration and policing strategy are unrelated.

“Chicago will not be blackmailed into changing our values, and we are and will remain a welcoming city,” Emanuel said.

“The federal government should be working with cities to provide necessary resources to improve public safety, not concocting new schemes to reduce our crime-fighting resources,” he added.

The Sun-Times has reported that in Chicago, there has been no known connection between undocumented immigrants and the spike in the city’s violent crime.

Johnson said he doesn’t want people in Chicago to avoid reporting crimes or making contact with police out of fear of their immigration status.

Under the new guidelines, the Justice Department also wants local jurisdictions to tell federal officials of an undocumented immigrant’s release from police custody at least 48 hours in advance. Legal experts say that request could cause police departments to hold people for longer than 48 hours, violating their constitutional rights.

Mary McCarthy, executive director of the National Immigrant Justice Center, called the Justice Department’s battle a “selfish choice.”

“History in the past six months has proven that the courts are really an important vehicle to ensure that the laws and policies in this country are constitutional and legal,” McCarthy said. “We can’t afford to lose that money.”

“It also is an issue of creating greater fear in the community,” she added.

Last week, Sessions said sanctuary cities make the country less safe.

“These policies are driven by politics and do not protect their citizens,” he said. “We will fight them with every lawful tool available.”

Chicago Corporation Counsel Ed Siskel, a former high-ranking Justice Department lawyer, said he doesn’t believe Sessions has the authority to add the requirements to a grant program created by Congress or to force local police departments to carry out federal immigration functions.

Contributing: Lynn Sweet