Texas and 15 other Republican-led states sued the Biden administration on Friday seeking to halt a new program that could give legal status to hundreds of thousands of undocumented immigrants who are married to U.S. citizens.

Filed just days after the program opened for applications, the lawsuit is the latest in a string of legal actions Texas has led challenging federal immigration policies and powers.

The suit, filed in the U.S. District Court for the Eastern District of Texas, seeks a temporary restraining order and preliminary injunction to immediately suspend the program.

In court filings, the states assert that the program is illegal because it exceeds the discretion that the executive branch has to set policy.

“The Biden-Harris Administration — dissatisfied with the system Congress created, and for blatant political purposes — has yet again attempted to create its own immigration system,” the 67-page court filing said.

“This agency action is nothing less than mass amnesty cloaked in purported executive discretion — a sweeping, last-minute ploy by an administration bent on rewriting immigration laws without Congress,” it said.

It also said that the program ran afoul of the law because it misused so-called parole, an authority exercised by the Homeland Security Department to allow people outside the United States to enter the country for urgent humanitarian reasons, on a case-by-case basis.

The Biden program was, instead, attempting “to parole aliens en masse,” who were already in the country, the motion said.

“Parole authority is not unbounded,” it added.

In a statement, Angelo Fernández Hernández, a White House spokesman, said that “Republican elected officials continue to demonstrate that they are more focused on playing politics than helping American families or fixing our broken immigration system.”

“The lawsuit aims to separate American citizens from their spouses and stepchildren who are already eligible for lawful permanent residency and could remain together through this process,” he said.

A spokeswoman for the Homeland Security Department, which is running the program, said that the agency would defend the program in court and continue to process new applications.

Under the new policy, up to 500,000 undocumented spouses could be shielded from deportation and given a pathway to citizenship and permission to work legally in the United States.

The program, announced on June 18 by President Biden, marked one of the most expansive actions to assist undocumented immigrants since Deferred Action for Childhood Arrivals, or DACA, was enacted 12 years ago to protect those who came to the United States as children.

In unveiling the program for undocumented spouses, Mr. Biden said that he was promoting family unity, which he called a core American value.

The program, which came soon after his administration imposed tough new restrictions on asylum, was seen a way to counter critics who said the asylum restrictions were too harsh.

The program aims to facilitate the legalization of undocumented spouses of Americans who have been living in the United States for more than a decade. Even though marrying an American citizen generally provides a pathway to U.S. citizenship, people who crossed the southern border illegally, rather than arriving with a visa, are required to return to their home countries to complete the process for a green card.

The new program allows them to skip that step, which can keep them apart from their loved ones for months or longer, and remain in the United States while they pursue legal status.

Immigrant-advocacy organizations swiftly condemned the lawsuit.

“This is a baseless legal attack, focused entirely on the politics of trying to go after immigrants and American families, against a highly popular and lawful policy,” said Todd Schulte, president of FWD.us, a pro-immigrant group.

“The only motivation behind this lawsuit is the cruelty of tearing families apart and the crass politics of hoping a judge might do the bidding of the anti-immigrant movement,” he said.

There are roughly 1.1 million undocumented immigrants married to American citizens in the United States, according to FWD.us, though most will not qualify for the program.

The lawsuit was filed by the states of Texas and Idaho along with 14 state attorneys general from Alabama, Arkansas, Florida, Georgia, Iowa, Kansas, Louisiana, Missouri, North Dakota, Ohio, South Carolina, South Dakota, Tennessee and Wyoming.

Hamed Aleaziz in Washington contributed reporting.