The mother of a suspected terrorist has lost a court challenge, meaning he and another man can be tried in the United States.
Shafee Elsheikh and Alexanda Kotey were captured more than two years ago by a Kurdish-led, US-backed militia.
The pair are accused of being Islamic State fighters and part of the all-British execution cell known as "The Beatles".
On Tuesday, the mother of Elsheikh lost a High Court challenge against Home Secretary Priti Patel’s decision to share evidence about her son with US authorities.
It paves the way for their transfer from Iraq to the US.
Analysis from Security Editor Rohit Kachroo
Two alleged Islamic State executioners are set to go on trial after a court ruling paved the way for their transfer to the US.
Alexanda Kotey and El Shafee Elsheikh, from west London, could be flown from Iraq within days to stand trial in Virginia next year.
It follows a decision this morning by a British court to lift a ban preventing the Home Office from supplying intelligence about the two alleged fighters to their American counterparts.
The two men are accused of being members of an all-British execution cell known by their hostages as ‘The Beatles’.
They are alleged to have taken part in the beheading of hostages, including British and American aid workers and journalists.
The group also included Mohammed Emwazi, known as “Jihadi John,” who was killed by a US drone stroke in 2015 and Aine Davis, who was jailed in Turkey.American authorities said last month that they would not seek the death penalty against the two fighters for their roles in Syria.
But in a letter to Home Secretary Priti Patel, the US Attorney General said that if the UK could not overcome the necessary legal hurdles to hand over evidence required for a trial to take place in the US, the pair would be transferred to Iraq for trial instead.
"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,” Bill Barr wrote.
A Home Office spokesperson confirmed that the evidence requested by American authorities had been shared with US prosecutors shortly after the court ruling.
“The Home Secretary has been clear throughout of her determination to deliver justice for the victims and their families," they said.
Last month, the US said it would not seek the death penalty against the men, leading to the UK agreeing to share information.
Previously the UK would not agree to the pair's extradition to the US due to the threat of the death penalty.
In their last TV interview before both were taken into custody by the US, Alexanda Kotey and El Shafee Elsheikh dodged the opportunity to directly apologise for the death of British aid worker David Haines.
ITV News Security Editor Rohit Kachroo carried out the last interviews on camera with the remaining 'Beatles' - Kotey and Elsheikh
He added he has "no problem apologising" for moving Mr Haines from location to location during his time in captivity.
Kotey, however, remained evasive when pressed by ITV News Security Editor Rohit Kachroo: "I won't forget what I've said before."
Before adding: "I find your line of questioning irritating."