Military Judge Postpones Guilty Plea Proceedings in Sept. 11 Case

A military judge on Sunday postponed a hearing to receive the guilty plea of Khalid Shaikh Mohammed, who is accused of masterminding the Sept. 11 attacks, so that prosecutors can seek again to nullify the plea deal.

Col. Matthew N. McCall, the judge, did not freeze preparations for the hearing, as prosecutors had requested. Instead, he told defense and prosecution lawyers to agree on a week or more next month or in early January to hold plea hearings at Guantánamo Bay, Cuba, for Mr. Mohammed and his co-defendants, Walid bin Attash and Mustafa al-Hawsawi.

The judge said it was “not reasonable to indefinitely delay” the entry of pleas in the case. He also told the sides to continue to collaborate on providing answers to questions related to clauses in the plea agreements. All three plea deals were reached July 31 and ostensibly withdrawn by Defense Secretary Lloyd J. Austin III two days later. On Wednesday, however, the judge ruled that Mr. Austin had acted too late and that the pleas were still valid, lawful contracts.

Colonel McCall made no mention of the fact that his next scheduled hearing, from Jan. 20 to Jan. 31, straddled the inauguration of President-elect Donald J. Trump — and most likely Mr. Austin’s departure from the Pentagon.

But a defense lawyer noted that the official who had approved the deal — an Austin appointee — was likely to leave the Pentagon at the end of the Biden administration and could potentially become unavailable for questions related to aspects of the plea deals.

In a rare Sunday hearing, Clayton G. Trivett Jr., the lead prosecutor, told the judge that the chief prosecutor for military commissions, Rear Adm. Aaron C. Rugh, had instructed his staff on Friday night to prepare an appeal of the judge’s decision reinstating the guilty pleas. Mr. Trivett asked the judge to halt all plea-related proceedings.