In a letter to Ms Patel, the US assured her the two British ISIS fighters will not face the death penalty if they are extradited to America to face trial. A UK court ruling had effectively stopped the sharing of evidence between the US and Britain unless the death penalty was removed. El Shafee Elsheikh and Alexanda Kotey, are both being held under charges of beheading Western hostages during their time with ISIS.
Mr Barr wrote in the letter: “On behalf of the United States Department of Justice, I am writing to provide an assurance that, if the United Kingdom grants our mutual legal assistance request the United States will not seek the death penalty in any prosecutions it might bring against Alexanda Kotey and El Shafee Elsheikh, and, if imposed, the death penalty will not be carried out.
“I know that the United Kingdom shares our determination that there should be a full investigation and a criminal prosecution of Kotey and Elsheikh.
“These men are alleged to be members of the terrorist group the Islamic State of Iraq and al-Sham and to have been involved in kidnappings, murders, and other violent crimes against the citizens of our two countries, as well as the citizens of other countries.
“If we receive the requested evidence and attendant cooperation from the United Kingdom, we intend to proceed with a United States prosecution.
ISIS news: US won’t seek death penalty
ISIS news: The two were transferred to US custody in October
“Indeed, it is these unique circumstances that have led me to provide the assurance offered in this letter.”
The two ISIS terrorists were captured by Kurdish forces two years ago.
US officials have not yet announced the charges against them.
They were transferred to US custody last October.
ISIS news: Alexanda Kotey
By giving assurances over the death penalty, the US hopes to receive valuable intelligence to be able to prosecute the two.
The two had been in a group with two other ISIS fighters and were believed to be responsible for the beheadings of more than 27 hostages.
Ringleader of the group, Mohammed Emwazi also known as Jihadi John was killed in a 2015 drone strike.
The final member, Aine Davis was imprisoned in Turkey.
ISIS: The pair were part of a four-man terrorist group
ISIS news: William Barr
The Daily Telegraph has claimed the US will move the men to Iraqi custody if the intelligence is not transferred by October 15.
However, Iraq still carries out the death penalty.
US and British authorities say the group had been responsible for 27 killings including James Foley.
Mr Foley’s mother, Diane said: “I feel that both countries ideally should work together to hold these men accountable and give them a fair trial.
“If they are guilty, they need to be put away for the rest of their lives.”
There has so far, not been any response from the UK Government.
ISIS news: Priti Patel received the letter
The ringleader of the group, Jihadi John first appeared in an execution video in 2014.
He was later seen in several other videos which showed the deaths of captives.