WASHINGTON — The Justice Department ramped up pressure Wednesday on so-called sanctuary cities seeking public safety grant money, warning that they could be legally forced to prove they are cooperating with federal immigration authorities. The move prompted immediate backlash, with mayors from across the country boycotting a planned meeting at the White House with President Trump on Wednesday afternoon.

Trump responded by accusing the boycotting mayors of putting the needs of “criminal illegal immigrants over law-abiding Americans.”

Officials sent letters to roughly two dozen jurisdictions threatening to issue subpoenas if they don’t willingly relinquish documents showing they aren’t withholding information about the citizenship or immigration status of people in custody.

The department has repeatedly threatened to deny millions of dollars in important grant money to communities that refuse to comply with a federal statute requiring information-sharing with federal authorities, as part of the Trump administration’s promised crackdown on cities and states that refuse to help enforce U.S. immigration laws.

Many cities have been openly defiant in the face of the threats, with lawsuits pending in Chicago, Philadelphia and California over whether the administration has overstepped its authority by seeking to withhold grant money.

The move angered members of the U.S. Conference of Mayors who had been set to meet with Trump on Wednesday to discuss infrastructure, drug addiction and other topics.

New Orleans Mayor Mitch Landrieu, the conference president, said in a statement that “the Trump administration’s decision to threaten mayors and demonize immigrants yet again – and use cities as political props in the process – has made this meeting untenable.”

“The U.S. Conference of Mayors is proud to be a bipartisan organization. But an attack on mayors who lead welcoming cities is an attack on everyone in our conference,” he said.

New York’s Bill de Blasio and Denver’s Michael Hancock announced their boycotts on Twitter.

“I will NOT be attending today’s meeting at the White House after (at)realDonaldTrump’s Department of Justice decided to renew their racist assault on our immigrant communities,” de Blasio wrote, adding that the move “doesn’t make us safer and it violates America’s core values.”

Hancock said he had “better things to do than be part of a photo op for 45 as he threatens cities again.”

Still, many mayors did attend. In remarks in front of the group, Trump blasted those who had boycotted.

“My administration is committed to protecting innocent Americans and the mayors who choose to boycott this event have put the needs of criminal illegal immigrants over law-abiding Americans,” he said.

Trump spokeswoman Sarah Huckabee Sanders added that if mayors have a problem with the Justice Department’s actions, “they should talk to the Congress, the people that pass the laws. The Department of Justice enforces them, and as long as that is the law, the Department of Justice is going to strongly enforce it.”

As for the mayors, she said the White House would love to work with them, “but we cannot allow people to pick and choose what laws they want to follow.”

“If we have a country with no laws, then nothing matters,” Sanders added.

The 23 jurisdictions that received letters Wednesday include cities in California, Illinois, Kentucky, Massachusetts, Mississippi, New Mexico, New York, Oregon, Vermont and Washington. Officials said the places were previously warned that they need to provide information about their policies to be eligible to receive grants that pay for everything from bulletproof vests to officer overtime.

Some local officials vowed to fight, like Seattle Mayor Jenny Durkan, a former U.S. attorney. Others pledged to cooperate, like California Attorney General Xavier Becerra, who said the jurisdictions in his state would have no trouble providing the new information showing that they are complying with federal law.

Attorney General Jeff Sessions has blamed “sanctuary city” policies for crime and gang violence, saying Wednesday, “we have seen too many examples of the threat to public safety represented by jurisdictions that actively thwart the federal government’s immigration enforcement–enough is enough.”

But defenders of sanctuary city practices say they actually improve public safety by promoting trust among law enforcement and immigrant communities and reserving scarce police resources for other, more urgent crime-fighting needs.