The Trump administration has finalized a new rule that could limit the number of legal immigrants living or coming into the United States by penalizing those who depend on food stamps or other public assistance.

The regulation, published in the Federal Register on Monday morning, will have the most immediate impact on low-income immigrants, who despite being here legally may have to choose between staying in America and accepting financial aid.

For more than a century, immigrants seeking to enter or live in this country have had to prove they will not become what is called a “public charge.” The administration has sought to dramatically expand the conditions of that test, saying the move would save taxpayers millions of dollars a year.

The new rule defines “public charge” as anyone who receives one or more public benefits for more than 12 months, in the aggregate, within any 36-month period.

People applying for visas to enter the country, or for green cards that permit legal permanent residency, could be denied if they are deemed likely to rely on government assistance. Accepting those kinds of benefits now or in the past would be a heavily weighted negative factor in determining whether they represent a public charge, The Inquirer has reported.

One immigrant-advocacy group in Washington has announced plans to file a legal challenge to block the rule, and others are expected to follow.

“We are crossing our fingers with respect to litigation that’s going to be happening,” said Cathryn Miller-Wilson, executive director of Philadelphia-based HIAS Pennsylvania, which works to help immigrants navigate American society.

Clients have been phoning the agency since the administration’s plans for the rule became public last fall, she said, and Monday’s news has only increased the tension.

It’s frustrating, Miller-Wilson said, because low-income immigrants are not a drag on the country. Just the opposite, they’ve proven decade after decade “to be hardworking people who create the next generation of CEOs.”

The administration says the new rule, which is to take effect in 60 days, promotes self-sufficiency and perseverance among migrants to this country.

U.S. Citizenship and Immigration Services acting Director Ken Cuccinelli said in a statement Monday that “President Trump has delivered on his promise to the American people to enforce long-standing immigration law.

"Throughout our history, self-sufficiency has been a core tenet of the American dream. Self-reliance, industriousness, and perseverance laid the foundation of our nation and have defined generations of hardworking immigrants seeking opportunity in the United States ever since. Through the enforcement of the public charge inadmissibility law, we will promote these long-standing ideals and immigrant success.”

The White House has pressed on multiple fronts to lower immigration, both legal and illegal, including the major Wednesday raid in Mississippi in which 680 immigrants were rounded up. In polls, immigration has consistently ranked as a top issue for GOP voters preparing for the 2020 presidential election.

It was not immediately clear how many people would be impacted by the new public-charge rule, which seems certain to be challenged in court.

The National Immigration Law Center, an advocacy organization in Washington, announced plans to file a lawsuit to try to block the rule. And California Attorney General Xavier Becerra tweeted, “We will not stand idly by while this administration targets programs that children and families across our state rely upon. We are ready to take legal action to protect the rights of all Californians.”

Immigration advocates say the rule could contribute to the separation of families, as some parents could be barred from staying in the country while their American-born, citizen children end up in foster care.

“Let’s call this rule what it is: a thinly veiled attempt to stratify immigration along income lines and to dissuade low-income and disproportionately black and brown immigrants from using financial assistance programs,” said Erin Hemlin, director of health policy and advocacy at Young Invincibles, a Washington-based advocacy group.

Doctors’ groups denounced the new rule, with the American Academy of Pediatrics calling it “a threat to the health of immigrant children and families.”

“The rule considers the use of public programs like Medicaid, the Supplemental Nutrition Assistance Program, and housing assistance in this definition, forcing immigrant families into an impossible choice: keep your family healthy but risk being separated, or forgo vital services so your family can remain together in this country,” interim CEO/executive vice president Mark Del Monte said Monday.

Many immigrants legally use government benefits to supplement low-wage work as they move up the economic ladder, according to the Legal Aid Society in New York, which said the Trump administration was attempting to demonize poorer migrants for political gain.

The rule enables the rejection of immigrants applying for permanent residency or for a temporary visa if they have used or seem likely to rely on certain forms of public assistance.

“This rule will dramatically change the lives of immigrants and the course of immigration to the U.S.,” said Ali Noorani, executive director of the National Immigration Forum. “If implemented, the rule will grant immigration officers the authority to punish immigrants for accessing services legally. These are programs and services that help us all get through a rough patch in life."