Donald Trump has doubled down on his hardline immigration stance with a mix of provocative humour and ominous warnings, praising a newly built migrant detention centre in the Florida Everglades — nicknamed "Alligator Alcatraz."

Speaking to reporters on Tuesday during his visit to the facility, the US president described the site as "surrounded by miles of treacherous swampland" and joked that "cops in the form of alligators" would help keep detainees in line.

"You don’t have to pay them so much," he said.

"If they escape prison, how to run away. Don’t run in a straight line. Run like this," he added, mimicking a zigzag motion.

"Your chances go up about one percent."

The detention facility — built on a former airfield and encircled by wetlands home to alligators and venomous snakes — is designed to house up to 1,000 undocumented migrants, with expansion plans for up to 5,000.

Trump described those expected to be held there as "some of the most vicious people on the planet."

Asked if the centre’s location was intended to deter escapees through the threat of being eaten, Trump replied, "I guess that’s the concept."

While protesters demonstrated near the site, Trump appeared unfazed, using the attention to further frame the centre as a deterrent.

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

The Republican also repeated controversial calls for mass deportations and suggested even naturalised American citizens with criminal records could be stripped of their status. "It’s controversial but I couldn’t care less," he said.

He described the influx of undocumented migrants under Democratic predecessor Joe Biden as "disgusting," and falsely equated most with "sadistic" gangs.

The facility has drawn criticism from environmentalists over its location in the Everglades — a protected conservation zone and major alligator habitat.

The state is home to an estimated 200,000 alligators, though fatal attacks are rare.

Trump’s remarks come amid wider efforts by his administration to portray a tough-on-migration stance, which has included sending some detainees to Guantanamo Bay and a mega-prison in El Salvador.

He also said a plan to reopen the original Alcatraz prison in California was still "on track," despite objections from state officials.