The judge in the first civilian trial of a former Guantanamo inmate has ruled that a key United States government witness cannot testify.
Ahmed Khalfan Ghailani, 36, denies helping al-Qaeda kill 224 people in two US embassy bombings in Africa in 1998.
The judge ruled the witness could not testify as he had been named by Mr Ghailani while he was "under duress".
New York Judge Lewis Kaplan has postponed Mr Ghailani's trial, which had been due to begin in a federal court in Manhattan on Wednesday. It is now due to open with jury selection on 12 October.
In his ruling, the judge said the proposed government witness had been identified during "statements made by Ghailani to the CIA under duress".
The BBC reports Hussein Abebe, was expected to testify that he had sold TNT used in the bombing of the US embassy Tanzania in August 1998 to Mr Ghailani.
Mr Ghailani was detained in Pakistan in 2004, taken to a secret CIA facility and then to Guantanamo Bay in 2006.
He is the first Guantanamo prisoner to be tried in the civilian courts. He faces life in prison if convicted.
The 1998 bombings of US embassies in Tanzania and Kenya killed 224 people.