Mayor Rahm Emanuel says Chicago will keep fighting President Trump's immigration policies with a federal lawsuit alleging it's illegal for the federal government to withhold public safety grants from so-called "sanctuary cities."

The mayor said Chicago won't "be blackmailed into changing our values, and we are and will remain a welcoming City."

The lawsuit will be filed Monday.

Chicago officials say there are new qualifications for a public safety grant requiring cities to share information with federal immigration authorities. City officials allege they're unconstitutional.

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Chicago received about $2.3 million in such grants last year, which have been used for buying police vehicles.

The city is being helped by two outside law firms on a pro bono basis.

Federal officials have threatened to withhold federal funding for sanctuary cities, saying they don't comply with federal laws.

Asked to comment on Emanuel's statement, U.S. Department of Justice spokesman Ian D. Prior said via email: "In 2016, more Chicagoans were murdered than in New York City and Los Angeles combined. So it's especially tragic that the mayor is less concerned with that staggering figure than he is spending time and taxpayer money protecting criminal aliens and putting Chicago's law enforcement at greater risk."

Meanwhile, in one high-profile immigration case unfolding in Los Angeles, a 42-year-old pastor was detained and could be soon deported.

Victoria Carias is praying her husband, pastor Noe Carias, will come home soon. He was recently detained by U.S. Immigration Customs Enforcement after living in the U.S. with his American-born wife and two young children.

"On my children, it's been its been very, very hard -- terrible. Emotionally, it's been very hard for them. They cry at night, they miss their father, I miss my husband deeply," Victoria Carias told CBS News correspondent Mireya Villarreal.

In a statement to CBS News, ICE said "Mr. Carias is a repeat immigration violator who assumed multiple identities" and "his actions have established a pattern or misrepresentation."

As a teenager, Noe Carias had several run-ins with ICE. He was granted two stays, but his third was denied last month.

The family's attorney, Noemi Ramirez, told Villarreal she thinks her client is "just a victim of the new administration."

Ramirez believes the president's promise to target criminals is far from what's happening in the field.

"The detentions, internally here in the United States, have increased 150 percent since the Obama administration," Ramirez said.

This week, President Trump rolled out a new immigration bill that restricts what kind of immigrant should be eligible for a green card.

In another Southern California case, Romulo Avelica, was detained after dropping his daughter off at school.

The Mexican citizen had been living in the U.S. for 25 years.

In the last nine months, ICE has made more than 102,000 immigration arrests and removed more than 171,000 people.

"I didn't feel like my family -- any one of us -- would be a priority for deportation. I never thought this could happen to us," Brenda Avelica told Villarreal.

Avelica's attorneys are trying to intervene, but as of this Monday, he's eligible for deportation. Pastor Carias had his green card application in when ICE picked him up. There's no word yet on when he'll get his hearing, Villarreal reports.