The alleged mastermind of the 9/11 attacks in 2001,
Khalid Sheikh Mohammed, will be tried by a military commission at Guantanamo Bay along with four other men.
The Obama administration had wanted them to be tried in a civil court but backed down in the face of fierce opposition.
Back in 2009 Obama had pledged to close Guantanamo Bay.
On Monday Whitehouse spokesman Jay Carney said:
“The President’s primary concern here is that the accused perpetrators of that terrible attack on the American people be brought to justice as swiftly as possible, and as fairly as possible.”
Last month Obama reluctantly lifted a two-year freeze on any new military trials at Guantanamo Bay in Cuba.
Much of the opposition to trying inmates in U.S courts was about security, as well as giving prisoners full U.S legal rights.