The Trump administration is making plans for an immigration crackdown in Chicago that would involve 200 homeland security officials and the use of a naval base outside the city as a staging area, according to internal documents obtained by The New York Times.

The request to use a Naval Station in Illinois, drafted in recent days by the Homeland Security Department, suggested that the Trump administration was planning a sustained operation, potentially for the month of September. The request, should it be granted by the Defense Department, would be a notable example of the nation’s military resources being used for civilian law enforcement by an administration that has increasingly blurred the line between them.

The city has long been a target of the Trump administration. In recent weeks, President Trump has called the city a “mess,” and immigration officials have clashed with city's leadership over Chicago’s status as a so-called sanctuary city, which generally refers to places that limit cooperation with agents looking to deport undocumented immigrants.

“Chicago still has a crime problem. So President Trump, again, made a promise to the American people he will make the country safe again,” said Tom Homan, Mr. Trump’s border czar. He said that there were “discussions” about using the base; he would not confirm how many people would be sent there.

Mayor Brandon Johnson of Chicago issued a blistering response to reports of the crackdown.

“This plan seems to be a rerun of their tactics in Los Angeles, where ICE agents were used as a pretext to justify further escalation by federal agents and National Guard troops,” he said in a statement. “We reject any attempts that put Chicagoans in danger as a means of furthering the president’s political ends.”

He said the city would “ensure that Chicagoans know their rights” and help families learn what to do if detained.