The Biden administration asked a federal appeals court on Tuesday to block a plea agreement for accused 9/11 mastermind Khalid Sheikh Mohammed that would spare him the risk of the death penalty in one of the deadliest attacks ever on the United States.

The Justice Department, on behalf of the Pentagon, on Tuesday asked an appeals court to block an effort to enforce plea deals reached with four accused conspirators of the Sept. 11, 2001,

The defendants involved in the potential plea deal include Khalid Sheikh Mohammed, the alleged mastermind of the 9/11 attacks.