Nearly two dozen groups, including religious leaders and the city’s biggest union, committed on Thursday to signing an amicus brief opposing Mayor Eric Adams’ request to suspend the city’s right-to-shelter rules for homeless single adults amid the ongoing migrant crisis.

The effort follows the mayor’s latest application to a state court to suspend the right to shelter as the city struggles to house more than 63,000 migrants who have entered the shelter system over the past year.

The coalition, known as New York Shelter for All in Need Equally, or NY SANE, was organized by Christine Quinn, who heads WIN, a homeless shelter provider for women and families. The new coalition sets up a battle between Adams and a list of well-established interest groups that have historically advocated for working-class New Yorkers and immigrants.

They include 1199 SEIU, the politically powerful health care union; the New York Immigration Coalition and two influential anti-poverty policy groups: the Community Service Society of New York and the Robin Hood Foundation.

“I think the mayor thought he was going to sneak this by,” Quinn said during a press conference in front of St. Bartholomew’s Church in Midtown. “That he was going to repeal the right to shelter, he was going to throw new arrivals out on the street, like they weren't human beings, and nobody was gonna notice.”

She and others were planning to send letters of protest to both Adams and Gov. Kathy Hochul, who is supporting the city’s attempt to revise the right to shelter.

Quinn, a former Democratic City Council speaker who ran for mayor in 2013, has increasingly clashed with Adams over his homeless and housing policies, spurring speculation that she may be interested in challenging him in a primary or pursuing another elected office.

When Gothamist asked Quinn about the matter on Thursday, she reiterated that she was not planning to run against Adams.

New York City is the only city that provides such a broad offer of shelter for homeless people.

Adams and Hochul have argued that the mandate is incentivizing migrants to come New York City, where up to 600 of them now arrive daily.

The mayor’s office did not immediately respond to a request for comment, but Adams has said he does not believe the 40-year-old right-to-shelter obligation was ever intended to address a humanitarian crisis.

“We can't have a rule that one can come from anywhere on the globe and come to New York City and remain in New York City as long as they want and taxpayers must pick up the cost,” Adams said during a recent interview on CBS News’ “Face the Nation.”

He has said the cost of caring for migrants would grow to $5 billion this year.

Adams recently returned from a tour of Latin America where he gave interviews to local media trying to discourage migrants from coming to the city.

But critics warn that weakening the city’s right to shelter would not achieve the mayor’s desired effect, but instead leave the most vulnerable without a place to go — a more pressing concern as the colder months approach.

“What it will do is cripple efforts after COVID and the struggle we went through then to bring commuters and tourists back to the city,” said David Jones, the president of the Community Service Society. “Because the city streets, as we've seen in San Francisco and other places, will be clogged with the homeless seeking to survive a brutal winter.”

Meanwhile, Hochul addressed the subject with reporters in her Manhattan office after holding a news conference touting the state’s efforts to move chronically homeless New York residents into housing with wraparound services.

She said she is committed to aiding the recent migrant arrivals, noting that the state has already put $1.7 billion toward the effort. But she said she has to deal in “pragmatic solutions,” and the current interpretation of the right-to-shelter mandate – coupled with the thousands upon thousands of new arrivals — is unsustainable.

“I think people have to understand, we cannot let there be an open invitation to the entire world to come to New York because that is not sustainable,” she said. “That's what we're talking about, is this interpretation that has been promulgated for the last year-and-a-half. It doesn't hold up any longer.”

Jon Campbell contributed reporting.