The high court learned about the UK Home Office's motivation at a hearing on a lawsuit filed by the mother of El Shafee Elsheikh, one of the suspects, the local newspaper reported.
UK Home Secretary Sajid Javid reportedly decided not to ask the United States for the reassurances that the suspects would not face death penalty to avoid "political outrage" on part of Washington.
The two suspected Daesh members that the states plan to prosecute have been identified as Elsheikh and Alexanda Kotey, raised in the United Kingdom.
Daesh is believed to have carried out almost 30 beheadings of US and UK citizens in the territory held by the terrorist group.
*Daesh (ISIL/ISIS/Islamic State) is a terrorist group banned in Russia