Donald Trump has repeatedly promised to carry out the “largest deportation operation in American history,” deploying federal, state and local law enforcement to arrest, jail and deport potentially millions of people living in the country without legal permission.

A militarized operation would depend on detention camps to hold people marked for removal, and would invoke a centuries-old law previously used to detain Japanese Americans during the Second World War.

President-elect Trump told NBC News on Thursday, two days after defeating his Democratic rival Kamala Harris, that he has “no choice” but to implement large-scale deportations when he takes office in January.

“It’s not a question of a price tag,” he said. “It’s not — really, we have no choice. When people have killed and murdered, when drug lords have destroyed countries, and now they’re going to go back to those countries because they’re not staying here. There is no price tag.”

He told NBC News that he wants to “make the border strong and powerful and, and we have to — at the same time, we want people to come into our country.”

“And you know, I’m not somebody that says, ‘No, you can’t come in.’ We want people to come in,” he said.

Using the full force of federal, state and local law enforcement agencies to identify, detain and deport millions of people living in the US without legal permission could cost more than $967 billion over 10 years, according to the American Immigration Council.

That is nearly the same amount that undocumented immigrants pay in federal, state and local taxes within a 10-year period, according to the Institute on Taxation and Economic Policy.

Undocumented immigrants paid federal, state, and local taxes of $8,889 per person in 2022, the group found. For every 1 million undocumented immigrants, public services receive $8.9 billion in tax revenue. Those immigrants, despite paying into government services like healthcare and Social Security, are not eligible for them.

The Institute on Taxation and Economic Policy said Trump’s plans would eliminate 22 percent of American farmworkers, 15 percent of construction workers, eight percent of service workers, eight percent of manufacturing workers and six percent of transportation workers.

“The idea that deportation helps US citizens has always been an illusion. It’s never worked before and it wouldn’t work this time,” the group wrote.

Immigrants rights groups across the country are preparing to launch legal battles to stop Trump’s plans, once in motion.

Trump has promised to be a “dictator on Day One” of his administration, when it comes to the US-Mexico border and oil production.

Among his first priorities in office is to immediately reinstate immigration policy from his first administration that was reversed under President Joe Biden, Trump adviser Jason Miller told CNN.

Stephen Miller, an architect of Trump’s anti-immigration agenda from Trump’s first term, is also expected to play a significant role in shaping the president-elect’s policy.

Trump’s allies have pushed for a mass deportation operation beyond the scope of undocumented immigrants who are accused of committing crimes, who will initially be targeted for removal under the president-elect’s early agenda.

The president-elect has signalled rescinding programs like Deferred Action for Childhood Arrival and ending legal status protections for tens of thousands of immigrants who fled violence and crises in their home countries, historically bipartisan policies steadily eroded by Republicans.

Miller has even said that the previous Trump administration launched a “denaturalization project” in his term. “In 2025, expect it to be turbocharged,” he wrote last year.

Tom Homan, Trump’s former Immigration and Customs Enforcement chief, is also expected to join the new administration. Trump suggested he would be returning during a campaign rally earlier this year. One day earlier, Homan promised to “run the biggest deportation force this country has ever seen.”