The self-styled mastermind of the September 11 attacks and four co-defendants told a military judge at Guantanamo yesterday that they wanted to confess and plead guilty.
The defendants said in a note to the judge that they made the decision on November 4, the day Barack Obama was elected to become the next US President.
Mr Obama has said he will shut down the widely condemned Guantanamo prison camp and try detainees in the regular US civilian or military courts rather than the special Guantanamo tribunals created by the Bush administration.
Several of the defendants had said at previous hearings that they welcomed martyrdom, and they may have felt that opportunity slipping away with Mr Obama's election.
The judge questioned the five, including Khalid Sheikh Mohammed, who has already said he planned the September 11 attacks "from A to Z," to ensure they understood the impact of their decision. All five could face the death penalty.