President Trump decided on Monday to scrap a Biden-era program that allowed migrants fleeing four troubled nations to fly to the United States and stay temporarily in the country, part of a sweeping first-day crackdown on immigration.

The program, known as humanitarian parole, introduced by the Biden administration in early 2023, allowed migrants from Cuba, Nicaragua, Haiti and Venezuela to fly to the United States if they had a financial sponsor and passed security checks. Migrants who entered under the program could stay for up to two years, unless they found other ways to stay long-term.

By the end of last year, more than 500,000 migrants entered the country through this initiative.

The program, which Mr. Trump ordered the head of the Department of Homeland Security to end, has served as one of two major legal avenues the Biden administration has established to try to deter migrants from entering the country illegally. Earlier on Monday, the Trump administration decided to close another program – a government application that allowed migrants to schedule appointments to enter the country at legal ports of entry.

“These processes — a safe and orderly way to reach the United States — have resulted in a significant reduction in the number of these individuals encountered at our southern border,” Alejandro N. Mayorkas, the Biden administration’s homeland security secretary, said last spring. “It is a key element of our efforts to address unprecedented levels of migration across our hemisphere.”

Republican lawmakers viewed the program as a way to give migrants who have no other access to the United States a chance to enter the country for up to two years and obtain work permits.

“Here’s an idea: Don’t fly millions of illegal aliens from failed states thousands of miles away into small towns across the American Heartland,” Stephen Miller, the architect of much of Trump’s immigration policy, said on social media in September.

Texas, along with other Republican states, sought and failed to end the program. But the Biden administration had already said in October that it would allow permits for migrants from the four countries to expire after two years, forcing hundreds of thousands of people to find other ways to stay in the country or face deportation.