(CBS) — The city of Chicago is threatening to sue the U.S. Justice Department, which has slapped conditions on a new grant the city hopes to use to hire additional police officers.

In a statement, Mayor Rahm Emanuel contended that complying with conditions for the $3.1 million grant would force the city to work with U.S. Immigration and Customs Enforcement officials and end its status as a sanctuary city.

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Emanuel said in doing so, the city would “abandon its values” but added they “are not for sale.”

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He said Chicago will remain “a welcoming city.”

A U.S. District Court judge in September issued a preliminary injunction against the Justice Department when it attempted to impose a similar condition on a different public safety grant.

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City Corporation Counsel Ed Siskel issued a statement that said the Justice Department “should stop playing games,” or face another court challenge.