San Salvador, El Salvador - El Salvador's iron-fisted leader on Monday offered to jail Americans so President Donald Trump can outsource the US prison system, an extraordinary step that was hailed by Secretary of State Marco Rubio.

There is virtually no precedent in contemporary times for a democratic country to send its own citizens to foreign jails, and any attempt to do so is sure to be challenged in US courts.

But Rubio welcomed an offer to do just that by President Nayib Bukele, whose sweeping crackdowns have won him hero status for many in President Donald Trump's orbit.

"He has offered to house in his jails dangerous American criminals in custody in our country, including those with US citizenship and legal residency," Rubio told reporters in San Salvador.

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"No country's ever made an offer of friendship such as this," Rubio said.

"We are profoundly grateful. I spoke to President Trump about this earlier today," he said.

Bukele said that El Salvador would ask for payment and was ready to incarcerate Americans in a prison he opened a year ago that is Latin America's largest.

"We have offered the United States of America the opportunity to outsource part of its prison system," Bukele wrote on X after Rubio's statement.

"The fee would be relatively low for the US but significant for us, making our entire prison system sustainable."

Rubio said that Bukele was also willing to take back Salvadoran citizens and nationals of other countries.

Rubio appeared to suggest the focus in El Salvador would be on jailing members of Latin American gangs, such as El Salvador's MS-13 and Venezuela's Tren de Aragua.

"Any unlawful immigrant and illegal immigrant in the United States who is a dangerous criminal – MS-13, Tren de Aragua, whatever it may be – he has offered his jails," Rubio said.

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Since his return to the White House last month, Trump has put a top priority on speeding up the deportation of millions of people in the US without documentation.

Trump has sought to crack down on the right to birthright citizenship, which is enshrined in the US Constitution.

Trump has also unveiled plans to detain 30,000 migrants at the US base in Guantanamo Bay, Cuba – a prison which previous Democratic presidents said they hoped to close.

The Trump administration is especially eager to deport Venezuelans.

Since taking office last month, Trump has stripped roughly 600,000 Venezuelans of protection from deportation ordered by his predecessor Joe Biden, citing the economic and security crisis in the South American country run by nemesis Nicolas Maduro.

Bukele's crackdown has included mass roundups of suspects without warrants and the opening of the maximum-security prison where he has offered to jail Americans.

The prison known as the "Terrorism Confinement Center," or CECOT, is surrounded by huge concrete walls on the edge of a jungle 45 miles southeast of San Salvador. It is designed to house 40,000 people, with around 15,000 estimated to be there now.

People incarcerated at CECOT leave their cells only when they have court hearings by video link from a room in the prison, or to exercise for 30 minutes per day in a large hallway.

Bukele's actions have faced criticism from human rights groups, including Amnesty International and Human Rights Watch.

Rubio's motorcade traveled an hour through the forests to Bukele's lakeside vacation home on Lake Coatepeque, with the 43-year-old president sporting sunglasses and sneakers as he showed the top US diplomat the sweeping view.

As people on a boat below cheered him, Bukele waved down to them and told Rubio with a grin – switching to English for a moment – "90% approval rating!"

Bukele's other fans include the president's son, Donald Trump Jr., and the right-wing populist journalist Tucker Carlson, who both attended his second inauguration last year.

The Trump administration has so far not touched the protected status from deportation of some 232,000 Salvadorans in the US, which was also extended by Biden.