The UK has been urged to take back two suspected ISIS members, from a group dubbed The Beatles, by a senior US military commander.
El Shafee Elsheikh and Alexanda Kotey are each accused of being part of a four-man group, given the nickname due to their British accents, suspected of 27 beheadings.
Major General Patrick Roberson, commander of US special ops, called on the UK to take back British Islamic State fighters.
Asked by the BBC whether Elsheik and Kotey should be repatriated to the UK, Maj Gen Roberson said: "We would certainly like them to be."
The Syrian Democratic Forces (SDF) and the US were "working very hard to make sure that the countries of origin get these foreign terrorist fighters back into their custody", he said.
Kotey and Elsheikh are accused of belonging to the cell which included Mohammed Emwazi, known as "Jihadi John", who was killed in a US air strike in 2015.
While the fourth supposed member was Aine Davis, who has been jailed in Turkey.
The group is suspected of involvement in numerous killings in Syria and Iraq, including those of British aid workers David Haines and Alan Henning as well as US citizens James Foley, Steven Sotloff and Peter Kassig.
Emwazi was filmed carrying out a number of the murders.
Videos of these were broadcast online.
Kotey and Elsheikh were raised in the UK and are believed to have been detained by Kurdish forces in Syria in January.
They have been stripped of their British citizenship.
The pair may face a federal trial in the US after the Crown Prosecution Service decided there was "insufficient evidence" for them to be tried in the UK.
Elsheikh's mother Maha Elgizouli has mounted a High Court challenge over the UK's sharing of evidence with US authorities.
This has been done under a "mutual legal assistance" agreement.
She says it was "unlawful" for the Government to do so unless it obtains assurances the pair will not face execution if convicted in the US.
Lawyers for Home Secretary Sajid Javid, who is contesting Ms Elgizouli's case, said it was not yet known whether the pair will be charged in the US,
However, they stated there is the "most powerful interest" in a proper investigation of their alleged crimes.
The case is being heard by the Lord Chief Justice Lord Burnett and Mr Justice Garnham.
They are expected to deliver their ruling at a later date.