America will not pursue the death penalty against two British ISIS Beatles detainees in exchange for vital evidence from the UK.
The promise to drop the capital punishment of El Shafee Elsheikh and Alexanda Kotey if found guilty, reverses two years of U.S. policy.
The move allows the men, who have had their British citizenship revoked, to stand trial in the States.
If the U.K. agrees to U.S. General Attorney Bill Barr's terms, it would cover all charges America might bring against the men.
"We would hope and expect that, in light of this assurance, the evidence can and will now be provided promptly," Barr wrote in a letter to Home Secretary Priti Patel.
"Time is of the essence. Further delay is no longer possible if Kotey and Elsheikh are to be tried in the United States, and further delay is an injustice to the families of the victims."
El Shafee Elsheikh, 32, and Alexanda Kotey, 36, are currently in U.S. custody in Iraq.
Moves to take them to the States for trial stalled for months.
In March, the Supreme Court ruled it was unlawful for the U.K. to share evidence with Washington without seeking assurances the pair will not face the death penalty.
Washington officials say they require crucial British evidence to help with their prosecution. Barr had previously opposed removing death as a possible sentence for the two men implicated in the beheadings of hostages.
A third Beatle is in prison in Turkey.
The fourth and most notorious member, Mohammed Emwazi - better known as "Jihadi John" - was killed in a U.S. drone strike in 2015.
Barr's decision has been described as "a fundamental shift in the discussion."
"This was the first breakthrough we've had in a long time. The sense was, 'We're going to get this done. We're going to get the diplomatic piece moving," one senior official said.
Elsheikh and Kotey have been held at Al Asad airbase in Iraq since October after a Turkish invasion of northern Syria led the U.S. military to move them from a prison in Syria run by allied Kurdish forces.
In June it emerged Kotey and Elsheikh, who was captured in early 2018, admitted they lied and that they did play a part in the detainment of American Kayla Mueller.
Previously they denied ever meeting the aid worker claiming "We didn't meet any foreign non-Muslims."
But the pair have now confessed they were involved in detaining Mueller who was tortured and sexually abused before her death in 2015.
In new interviews, both Kotey and Elsheikh attempt to distance themselves from the abuse and killings attributed to them as prison guards, calling themselves "liaisons" to the hostages.
However, each admitted beating captives and playing a role in facilitating communication with their families to extract ransoms.
Two years ago, when asked about Mueller, Elsheikh replied "Who?". Kotey added: "We didn't meet any foreign non-Muslims."
