The United States will not seek the death penalty in the prosecution of two Islamic State (IS) members suspected in the killing of American hostages, US Attorney General William Barr said, as long as the United Kingdom hands over evidence key to putting them behind bars.

“Time is of the essence,” Barr wrote in a letter to UK Home Secretary Priti Patel obtained by Al-Monitor. “We would hope and expect that, in light of this assurance, the evidence can and will now be provided promptly.”

Barr’s announcement, which was first reported on by Defense One, paves the way for the two governments to resume intelligence cooperation on the case. The United Kingdom, where suspects El Shafee Elsheikh and Alexanda Kotey are from, has hundreds of witness statements and intelligence intercepts collected on the two men, who make up half of the notorious IS cell dubbed the “Beatles."

The UK government initially handed over some evidence without assurances on the death penalty, but Elsheikh’s mother filed a lawsuit to stop further evidence-sharing with a country where capital punishment is a possible outcome. The British Supreme Court ruled in March that the former home secretary’s decision to share information had breached the country’s data protection law.