Chicago Mayor Rahm Emanuel says the city plans to sue the U.S. Department of Justice over President Donald Trump’s immigration policies, specifically over the so-called sanctuary cities program.

Emanuel made the disclosure Friday, while being interviewed for a Chicago radio program. The full interview is scheduled to air Sunday evening on WLS radio in Chicago, the Chicago Tribune reported.

The mayor, a Democrat who previously served as a congressman and as White House chief of staff under President Barack Obama, said the federal lawsuit will be filed Monday.

The suit will claim that it’s illegal for Attorney General Jeff Sessions to withhold federal Byrne grants from cities the Trump administration believes aren’t cooperating enough with U.S. Immigration and Customs Enforcement officials, the mayor said.

Chicago this year expects to receive $3.2 million from the Byrne grant program, money mostly used to buy police vehicles and other equipment, the Tribune reported. The grants are named for Edward Byrne, a New York City police officer who was murdered in 1988.

“We are not going to be between picking our values of who we are as a welcoming city, and strengthening our police department,” Emanuel said in the interview.

In filing the suit, Emanuel is likely trying to court support from Chicago’s Latinos, who are wary of the Trump administration’s immigration policies, as well as gain clout among other big-city Democratic mayors as they try to block Trump initiatives, the newspaper reported.

The Justice Department declined to comment on Emanuel’s comments Friday.

On Thursday, Fox News reported that Sessions threatened to withhold anti-crime funding from four cities – Baltimore; Albuquerque, New Mexico; and Stockton and San Bernardino, California – if they did not begin to cooperate more thoroughly with federal immigration officers.