The United States said Friday it was terminating the legal status of hundreds of thousands of immigrants, giving them weeks to leave the country.

President Donald Trump has pledged to carry out the largest deportation campaign in US history and curb immigration, mainly from Latin American nations.

The order affects around 532,000 Cubans, Haitians, Nicaraguans and Venezuelans who came to the United States under a scheme launched in October 2022 by Trump's predecessor Joe Biden and expanded in January the following year.

They will lose their legal protection 30 days after the Department of Homeland Security's order is published in the Federal Register, which is scheduled Tuesday.

That means immigrants sponsored by the program "must depart the United States" by 24 April unless they have secured another immigration status allowing them to remain in the country, the order says.

Welcome.US, which supports people seeking refuge in the United States, urged those affected by the move to "immediately" seek advice from an immigration lawyer.

The Processes for Cubans, Haitians, Nicaraguans, and Venezuelans (CHNV) program, announced in January 2023, allowed entry to the United States for two years for up to 30,000 migrants per month from the four countries, which have grim human rights records.

Biden touted the plan as a "safe and humane" way to ease pressure on the crowded US-Mexico border.

But the Department of Homeland Security stressed Friday that the scheme was "temporary."

"Parole is inherently temporary, and parole alone is not an underlying basis for obtaining any immigration status, nor does it constitute an admission to the United States," it said in the order.

Nicolette Glazer, an immigration lawyer in California, said the order would affect the "vast majority" of the half a million immigrants who entered the United States under the CHNV scheme.

"Only 75,000 affirmative asylum applications were filed, so the vast majority of the CHNV parolees will find themselves without status, work permits, and subject to removal," she posted on X.

"The chaos will be unreal".

Trump last weekend invoked rare wartime legislation to fly more than 200 alleged members of a Venezuelan gang to El Salvador, which has offered to imprison migrants and even US citizens at a discount.

More than seven million Venezuelans have fled their country over the last decade as the oil-rich country's economy implodes under leftist leader Nicolas Maduro, a bugbear of Washington who has faced major sanctions.