Man deported in error 'traumatised' by jail: US senator

US senator Chris Van Hollen met the El Salvadoran man mistakenly deported and being held in a prison in El Salvador at a hotel after initial requests to meet with him were denied, the Democratic lawmaker says.

Van Hollen said Kilmar Abrego Garcia was brought to his hotel before Van Hollen left the country on Thursday after he had tried to go to the notorious CECOT prison for gang members, where Abrego Garcia had been held.

The Maryland senator told a news conference in Washington that he and the lawyer for Abrego Garcia's family were pulled over by soldiers 3km outside the prison and told they were not allowed to proceed further.

El Salvadoran officials later brought Abrego Garcia, a resident of Maryland, to the hotel where Van Hollen was staying.

The case has pitted a defiant Trump administration against the courts, including the Supreme Court, raising the prospect of a constitutional conflict after the government acknowledged he was deported because of an administrative error.

Van Hollen said Abrego Garcia told him he was "traumatised by being at CECOT", and that he had been put in a cell with 25 other people for weeks and had not spoken to anyone outside of the jail since being detained.

The senator on Thursday posted on X an image of himself in El Salvador with Abrego Garcia.

Abrego Garcia told the senator that eight days earlier, he had been moved to another detention centre where conditions were better, but he still was unable to make contact with the outside world.

Van Hollen said the Trump administration, which has refused to adhere to a Supreme Court order to facilitate Abrego Garcia's return, and El Salvador's government needed to be held accountable for complicity in illegally holding him.

"This case is not only about one man, as important as that is. It is about protecting fundamental freedoms and the fundamental principle in the constitution for due process that protects everybody who resides in America," he said.

Van Hollen said the Trump administration had offered to pay El Salvador $US15 million ($A23 million) to hold its migrants in the prison, and had spent $US4 million so far.

He said that when he asked El Salvadoran Vice-President Felix Ulloa why Abrego Garcia was held at CECOT, he responded it was "because the Trump administration is paying us to keep him here".

The lawmaker told reporters that El Salvadoran officials had planned to hold the meeting by the hotel's swimming pool to contradict the narrative that Abrego Garcia was being held in harsh conditions.

He also disputed a social media post by President Nayib Bukele showing glasses with margaritas at the table where Van Hollen and Abrego Garcia sat, which he said the men were "sipping".

"This is the lengths that President Bukele will go to deceive people about what's going on," Van Hollen said.