The Biden administration has asked a federal appeals court to block a plea agreement for accused 9/11 mastermind Khalid Sheikh Mohammed and two co-defendants that would spare them the risk of the death penalty.

The Justice Department argued in a brief filed with a federal appeals court in the District of Columbia that the government would be irreparably harmed if the guilty pleas were accepted.

It said the government would be denied a chance for a public trial and the opportunity to “seek capital punishment against three men charged with a heinous act of mass murder that caused the death of thousands of people and shocked the nation and the world”.

The military judge at Guantanamo Bay and a military appeals panel rejected Defence Secretary Lloyd Austin’s effort to throw out the plea agreement, saying he had no power to do so after the senior Pentagon official for Guantanamo approved it in July.

Mohammed was due to enter his guilty plea on Friday and his two co-defendants next week.

The Justice Department brief said the defendants, by contrast, would not be harmed by a short delay, given that the prosecution has been ongoing since 2012 and the plea agreements would likely result in them serving long prison sentences, potentially for the rest of their lives.

“A short delay to allow this court to weigh the merits of the government’s request in this momentous case will not materially harm the respondents,” the government argued.