The US will not seek the death penalty against two British Islamic State fighters dubbed the “Beatles” who are suspected in the beheadings of Western hostages.

In a letter to Home Secretary Priti Patel, America’s attorney general William Barr said “time is of the essence” in seeking to prosecute the pair and “further delay is an injustice to the families of the victims”.

The decision could allow Britain to begin sharing evidence with federal prosecutors in the US for any potential case against El Shafee Elsheikh and Alexanda Kotey.

The men are suspected of being part of IS
Image: Kotey and Elsheikh were captured two years ago by a Kurdish-led, US-backed militia

An earlier UK court ruling had effectively blocked the sharing of evidence without US assurances that the death penalty was off the table.

“I know that the United Kingdom shares our determination that there should be a full investigation and a criminal prosecution of Kotey and Elsheikh,” Mr Barr wrote in the letter.

“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 a prosecution is to go forward in the United States, 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.”

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Mr Barr said the US will move forward with plans to transfer Kotey and Elsheikh to Iraq for prosecution if any legal objections in the UK are not resolved by 15 October.

The notorious group of IS fighters, who became known as “The Beatles” due to their British accents, are believed to be responsible for beheading more than 27 hostages.

Elsheikh and Kotey were captured two years ago by a Kurdish-led, US-backed militia, following the death of ringleader Mohammed Emwazi – known as “Jihadi John” – in a 2015 drone strike and the imprisonment of Aine Davis in Turkey.

US officials have not announced any charges against Elsheikh and Kotey but they have spoken publicly about their desire to see members of the cell face justice.

The pair were transferred to US custody last October.

Last month it was reported that the two men had further incriminated themselves in mistreating Western hostages in Syria.

In interviews obtained by NBC News, they were said to have admitted for the first time their involvement in the captivity of Kayla Mueller, an American aid worker who was held captive and tortured and sexually abused before her death in 2015.

Kayla Mueller 26-year-old American humanitarian worker from Arizona
Image: Aid worker Kayla Mueller was killed in 2015

US and British authorities say “The Beatles” were responsible for 27 killings, including the beheadings of Americans James Foley, Steven Sotloff and Peter Kassig, and British aid workers David Haines and Alan Henning.

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.”

In March, the UK’s Supreme Court held that it was unlawful for Britain to provide evidence to a foreign country that could be used in a death penalty prosecution.