WASHINGTON, D.C. — The Biden administration succeeded Thursday in temporarily blocking accused 9/11 mastermind Khalid Sheikh Mohammed from entering a guilty plea in a deal that would spare him the risk of execution for al-Qaida's Sept. 11, 2001, attacks.

It is the latest development in a long struggle by the US military and successive administrations to bring to justice the man charged with planning one of the deadliest attacks ever on the United States. It stalls an attempt to wrap up more than two decades of military prosecution beset by legal and logistical troubles.