On Thursday, Miami became the first major U.S. city to say it would change its practices regarding immigrants who are in the country illegally following President Donald Trump’s executive order cracking down on “sanctuary cities.” The executive order, signed Wednesday, threatened to cut federal grants for any cities or counties that don’t fully cooperate with Immigration and Customs Enforcement

Miami-Dade Mayor Carlos Gimenez ordered county jails to comply with federal requests to detain immigrants, the Miami Herald reports, saying the region stands to lose millions of dollars in federal funding otherwise.

There is no official definition for sanctuary cities, and standards differ across the country. Some cities instruct police not to ask about immigration status, issue ID cards to undocumented immigrants or simply refuse to hold undocumented immigrants already in custody until federal officials can start deportation proceedings.

While Miami-Dade has never declared itself a sanctuary city, since 2013 the city has refused to detain inmates wanted by ICE because the federal government doesn’t fully reimburse the county for the expenses. Miami-Dade is listed as a sanctuary city by the Department of Justice, but is working to change that status.

In a brief three-paragraph memo, Gimenez told Daniel Junior, the interim director of the Corrections and Rehabilitation Department, to honor all immigration detainer requests received from the Department of Homeland Security. Last year, the county declined to hold about 100 inmates wanted by the feds, which would have cost the county about $52,000 out of its total annual budget of $7 billion. The county receives about $355 million in federal funds.

“I want to make sure we don’t put in jeopardy the millions of funds we get from the federal government for a $52,000 issue,” Gimenez, a Republican who says he voted for Hillary Clinton, told the Herald. “It doesn’t mean that we’re going to be arresting more people. It doesn’t mean that we’re going to be enforcing any immigration laws.”

Several Democratic mayors of large U.S. cities were quick to promise to shield immigrants following Trump’s announcement this week.

“We’re gonna stay a sanctuary city,” Chicago Mayor Rahm Emanuel said in a news conference Wednesday. “There is no stranger among us. We welcome people, whether you’re from Poland or Pakistan, whether you’re from Ireland or India or Israel and whether you’re from Mexico or Moldova, where my grandfather came from, you are welcome in Chicago as you pursue the American dream.”

Boston Mayor Marty Walsh called the president’s executive orders “a direct attack on Boston’s people” and went so far as to say the city would shelter immigrants in City Hall. “We will not be intimidated by the threat to federal funding. We have each other’s backs and we have the constitution of the United States of America on our side,” said Walsh.

According to the Migration Policy Institute, Miami-Dade has more than 1.3 million immigrants, making it the county with the second-highest number of immigrants in the country. The other top two counties, Los Angeles County and Cook County (Chicago), are home to major sanctuary cities. Both Los Angeles Mayor Eric Garcetti and Emanuel have pledged to remain sanctuary cities.