Khalid Sheikh Mohammed, the alleged mastermind behind the September 11, 2001, terrorist attacks in the United States, is scheduled to face trial alongside three alleged co-conspirators in June 2028.

The trial date was set on Wednesday by US Air Force Judge Lieutenant Colonel Michael Schrama, following more than 20 years of legal proceedings and delays surrounding the case.

Mohammed and the other defendants — Walid Muhammad Salih Mubarak bin ‘Atash, Mustafa Ahmed Adam al Hawsawi and Ali Abdul Aziz Ali — have been held at the US detention facility at Guantanamo Bay, Cuba, over their alleged roles in the September 11 plot.

According to the judge’s scheduling order, jury selection through a military panel is expected to begin on June 5, 2028. Opening arguments are scheduled to follow about 30 days after the panel is seated.

The prosecution will then present its evidence, after which the defence will have an opportunity to make its case. The proceedings will eventually move to sentencing.

Judge Schrama rejected an earlier proposal from prosecutors to commence the trial in January 2027, determining that additional time was required to address outstanding pretrial evidence and compliance issues.

The latest timetable follows a series of setbacks in the long-running case. A US appeals court recently blocked plea agreements that would have allowed Mohammed and two other defendants to plead guilty without facing the death penalty.

The agreements had initially been approved by the official responsible for overseeing the Pentagon’s Guantanamo military commissions. However, they were subsequently withdrawn by then-US Defence Secretary Lloyd Austin amid opposition from Republican lawmakers.

Mohammed is accused of helping plan and coordinate the hijacking of four commercial passenger aircraft on September 11, 2001. Two of the planes were crashed into the World Trade Center in New York, while another struck the Pentagon in Arlington, Virginia.

The attacks resulted in the deaths of nearly 3,000 people and became one of the deadliest terrorist attacks in US history.

The Guantanamo Bay detention facility was established by the administration of former US President George W. Bush in 2002 to hold foreign terrorism and militant suspects following the September 11 attacks.

If the latest schedule remains unchanged, Mohammed and his three co-defendants will go to trial more than two decades after they were detained in connection with the case.