"Effective immediately, in the exercise of my authority, I hereby withdraw from the three pre-trial agreements," Austin wrote in a memo.

This development came within two days since Khalid Sheikh Mohammed, and two of his accomplices, held at the US military prison at Guantanamo Bay in Cuba, agreed to plead guilty. Austin on Friday also relieved Susan Escallier, the person in-charge of the Pentagon's Guantanamo war court, of her authority to reach pre-trial agreements in the case and took on the responsibility himself.

Earlier, several prominent Republican legislators including House of Representatives Speaker Mike Johnson and Senate Minority Leader Mitch McConnell strongly criticised the plea deals.

Mohammed, whom the U.S. described as the mastermind of the devastating attack that crashed a hijacked passenger planes into the World Trade Center, the Pentagon and a Pennsylvania field on September 11, 2001 attacks killing nearly 3,000 people.

Reportedly he is the most well-known inmate at the Guantanamo Bay facility, which was set up in 2002 by then-US President George W Bush.

According to a Pentagon statement, besides Mohammed, plea deals were also reached by two other detainees: Walid Muhammad Salih Mubarak Bin 'Attash and Mustafa Ahmed Adam al Hawsawi.