US President Donald Trump toured a new Florida migrant detention centre dubbed "Alligator Alcatraz" on Tuesday, boasting about the harsh conditions and joking that the reptilian predators will serve as guards.

The US$450 million camp has been built on a disused airfield deep in the Florida Everglades and is surrounded by swamps that are home to creatures including alligators and poisonous snakes.

"Very soon this facility will house some of the most menacing migrants, some of the most vicious people on the planet," Trump told reporters.

"We're surrounded by miles of treacherous swampland and the only way out is really deportation."

The steaming hot, mosquito-infested site is a symbol of the Republican administration's determination to look tough as it pursues its policy of mass deportations of undocumented migrants.

The name "Alligator Alcatraz" is a reference to Alcatraz Island, the former prison in San Francisco, that Trump recently said he wanted to reopen.

Protesters against "Alligator Alcatraz" held the latest in a series of demonstrations outside the site as Trump visited on Tuesday, but the Republican embraced the controversy.

"A lot of bodyguards and a lot of cops in the form of alligators – you don't have to pay them so much," Trump said.

"I wouldn't want to run through the Everglades for long. It will keep people where they're supposed to be."

Florida's Republican Governor Ron DeSantis, who greeted Trump on the tarmac, said "we want to cut through bureaucracy... to get the removal of these illegals done."

The 79-year-old Trump admiringly looked at bunk beds in cages made of metal fencing at the facility, which is built to house 1,000 people, but could later be expanded to house 5,000.

When asked earlier in the day if the idea behind the detention centre was that people who escaped from it would get eaten by alligators or snakes, Trump answered "I guess that's the concept."

Making a zigzagging motion with his hand, he quipped to reporters at the White House: "We're going to teach them how to run away from an alligator, okay?

"If they escape prison, how to run away. Don't run in a straight line. Run like this. And you know what? Your chances go up about one percent."

But after the quips, Trump later embarked on one of his dark diatribes about immigration, saying that he eventually wanted to start deporting criminals who had been naturalised as Americans.

"It's controversial but I couldn't care less," he said. (AFP)