The alleged mastermind of the September 11 terrorist attacks, Khalid Sheikh Mohammed, is to stand trial in New York in a civilian court, the United States has confirmed.
In 2001, two hijacked planes crashed into the World Trade Center's Twin Towers in lower Manhattan, killing nearly 3,000 people. Another plane crashed into the Pentagon in Washington DC, while a fourth crashed into a field in Pennsylvania.
The US military says Khalid Sheikh Mohammed has admitted planning the attacks.
Attorney-General Eric Holder announced on Friday that Mr Mohammed would be transferred from a US prison camp in Guantanamo Bay, Cuba, with four other men suspected of involvement.
Two Yemenis, a Saudi and a Pakistani-born Kuwaiti are accused of helping plan and finance the attacks.
Mr Holder says all will get a fair trial. The US government plans to seek the death penalty if any are convicted.
Until now, the accused have been facing prosecution at US military commissions in Guantanamo. The government had faced a 16 November court deadline to decide how to proceed in their cases.
The move is part of US President Barack Obama's effort to close Guantanamo, but some relatives of 9/11 victims say they oppose a federal court trial, the BBC reports.
Responsibility for the case will go to the Southern District of New York, with proceedings taking place near Ground Zero where the high-rise buildings collapsed.
Speaking in Tokyo ahead of Mr Holder's announcement, Mr Obama said Mr Mohammed would face "most exacting demands of justice".
Khalid Sheikh Mohammed has been described by US investigators as "one of history's most infamous terrorists".
Believed to be the number three al-Qaeda leader, he was captured in Pakistan in March 2003. He told a pre-trial hearing at Guantanamo in December 2008 that he wanted to plead guilty to all charges against him.
But intelligence memos released earlier this year revealed he had been subjected to harsh interrogation techniques, including water-boarding, on multiple occasions since his capture - potentially rendering some evidence inadmissible.