James Clapper had initially said the attack was spontaneous, but a spokesman for Clapper said in a statement Friday the initial assessment had been wrong, McClatchy Newspapers reported.
"In the immediate aftermath [of the assault], there was information that led us to assess that the attack began spontaneously following protests earlier that day at our embassy in Cairo," spokesman Sean Turner said. "As we learned more about the attack, we revised our initial assessment to reflect new information indicating that it was a deliberate and organized terrorist attack carried out by extremists."
U.S. Ambassador Christopher Stevens and three other American workers were killed in the attack.
President Mohamed Magariaf, head of Libya's interim government, challenged the initial assessment, saying the attack was organized and planned by foreigners, some with links to al-Qaida, and timed for the anniversary of the Sept. 11, 2001, terrorist attacks in the United States.
Witnesses interviewed after the attack described it as complex and well-organized and said it had not been preceded by a protest.
Matthew Olsen, director of the National Counterterrorism Center, was the first administration official to confirm the planned attack when he appeared before a Senate committee Sept. 19, McClatchy said.