The Chicago Police Department has said it will not assist with looming deportations by United States Immigration as ordered by President Donald Trump. The statement comes on Monday, a day after Chicago Mayor Brandon Johnson doubled down on his vow to oppose Trump’s sweeping reform.

Details of planned immigration raids are unclear, but they would be the opening step in the president-elect’s goal of overseeing the largest deportation program in history.

President-elect Donald Trump’s incoming border czar vows that the biggest city in the Midwest will be “ground zero” for mass deportations, and officials across the political spectrum in Chicago are bracing for a showdown.