The Biden administration on Friday issued sweeping extensions of deportation protections for hundreds of thousands of people from Sudan, Ukraine and Venezuela, a move that makes it nearly impossible for President-elect Donald J. Trump to quickly revoke the benefits when he takes office.

The extension of Temporary Protected Status, as the program is called, allows immigrants to stay in the country with work permits and protection from deportation for another 18 months after the current protection expires in the spring. Late last year, Secretary of State Antony J. Blinken recommended expanding the protections in a series of letters.

For decades, Democratic and Republican administrations have designated protections for citizens of countries in turmoil and deemed unsafe to return to. President Biden expanded the number of people who could be granted status as war broke out in Ukraine and instability gripped countries like Venezuela and Haiti.

“These designations are based on careful review and interagency collaboration to ensure that those affected by environmental disasters and instability receive the protections they need while continuing to make meaningful contributions to our communities,” Homeland Security Secretary Alejandro Mayorkas said in a statement.

Mr Trump has derided the program and vowed to end it, at least for certain countries. Immigrant advocates have asked the Biden administration to expand it to many of those countries before he takes office.

In his first term, Mr. Trump revoked the status of about 400,000 people from El Salvador and other countries, and then faced legal challenges.

According to the Congressional Research Service, more than 1 million migrants from countries in Latin America, the Caribbean, Africa, and the Middle East had temporary protected status as of 2024.

The move makes it legally harder for Mr. Trump to end the protections for citizens of the four countries, at least until they expire in 2026.

“Because President Biden has extended protections for citizens of all these countries, President Trump will not be able to deport these people anytime soon,” said Steve Yale-Loehr, an immigration expert at Cornell Law School.

“Trump cannot ignore what Congress wrote into law in 1990,” he said.

About 600,000 Venezuelans who currently have protections will be able to renew and remain in the United States by October 2026, and approximately 232,000 immigrants from El Salvador will be able to do so. More than 100,000 Ukrainians will be able to stay in the United States through August 2026. About 1,900 people from Sudan will also be able to renew their status.

The program was signed by President George HW Bush to ensure that foreign nationals already in the United States can remain in the country if it is unsafe for them to return to their home country due to a natural disaster, armed conflict, or other unrest.

During the campaign, JD Vance, the vice president-elect, called the program illegal when he criticized Haitians who settled in his home state of Ohio and benefited from it. Haiti is going through political turmoil and gang violence, and about 200,000 of its citizens are protected from removal under TPS until early 2026.

“We will end the mass granting of temporary protected status,” Mr. Vance said in October.

Critics have argued that temporary protection is repeatedly extended and serves as a de facto means of allowing people to stay in the country indefinitely, contrary to its intention to be a short-term solution.

While the program has become anything but permanent for many immigrants, it also highlights how troubled many parts of the world are and the failure of Congress to pass legislation to update America’s immigration system to the realities of contemporary global migration.

Immigrants from several countries, including El Salvador, Honduras and Nicaragua, have been eligible for protection for more than two decades. Other countries, such as Ethiopia, Lebanon and Syria, were added recently.

Gonzalo Roa, 43, a Venezuelan beneficiary, said he was worried about the fate of the program.

“It’s great news that it’s being rebuilt,” said Mr. Roa, who lives in Columbus, Ohio. He works in a car dealership and runs a small restaurant with his wife.

Without temporary status, Mr. Roa said, he would lose his job at the embassy and his two Venezuelan-born children would not be eligible for college scholarships and other benefits that legal status requires.