WASHINGTON (AFP) - The United States will not pursue the death penalty against two members of a notorious Islamic State in Iraq and Syria (ISIS) kidnapping and murder unit dubbed the Beatles, Attorney-General Bill Barr said in a letter released by the Justice department on Wednesday (Aug 19).

Barr wrote to British Home Secretary Priti Patel that Alexanda Kotey and El Shafee Elsheikh, who allegedly took part in grisly videotaped beheadings of Westerners, including journalists and aid workers, would be spared execution if placed on trial in the United States.

Barr made the pledge to be able to secure crucial evidence against the two Britons, now stripped of their citizenship, that has been withheld by the British government due to the chance they would face capital punishment, which is outlawed in Britain.

"If imposed, the death penalty will not be carried out," he said in the letter, dated Tuesday.

GRISLY BEHEADINGS

The United States is believed preparing to try the two for the murder of journalists James Foley and Steven Sotloff, and aid worker Peter Kassig, among possible others, during a period in 2014-2015 when the ISIS used their deaths as propaganda.

Kotey and Elsheikh were part of a four-member kidnapping gang within the Islamic State group dubbed "the Beatles" by their captives due to their British accents.

Kotey and Elsheikh are now being held by US forces in Iraq after their capture.

Britain has refused to assume responsibility for the two, not wanting to risk domestic turmoil by repatriating them, despite the group's victims including British aid workers David Haines and Alan Hennings.

But British public resistance due to the US death penalty and a court ruling have led to a two-year impasse in cooperation on the case.

"If a prosecution is to go forward in the United States," Barr wrote, "our prosecutors should have the important evidence that we have requested from the United Kingdom available to them in their efforts to hold Kotey and Elsheikh responsible for their terrorist crimes."

"We would hope and expect that, in light of this assurance, the evidence can and will now be provided promptly."

Last year, Elsheikh, who was born in Sudan, told an ITV television team that he wanted to stand trial in Britain.

"If the UK wants to put me on trial then I will defend myself with what I can," he said, while still being held in a prison camp in northern Syria where he and Kotey were captured.

"I will admit to what I admit to, and defend myself on what I defend myself on," he said.

Elsheikh added that he had "never committed a crime in the United States" and "has nothing" there.

FAMILY PRESSURES FOR TRIAL

Washington has been frustrated that European countries have mostly declined to take legal responsibility for their citizens who joined ISIS and are now held by the thousands in camps in Iraq and Syria.

Last month, the parents of Foley, Kassig, Sotloff and Kayla Mueller, who died in ISIS captivity, wrote in the Washington Post that the US government needs to move quickly to put the killers on trial.

Not mentioning the death penalty issue, they said there should be no further delay in bringing the accused to justice.

"We want to see our children's murderers held accountable. These things can happen only if the suspects are put on trial before a jury in an American court of law," they wrote.