U.S. Ambassador to Libya Christopher Stevens and members of his staff died in an attack on the U.S. consulate in Benghazi last week.
White House spokesman Jay Carney said Thursday that it was "self-evident" the incident was a terrorist attack.
"We have no information at this point that suggests that this was a significantly preplanned attack but this was the result of opportunism, taking advantage of and exploiting what was happening as a result of reaction to the video that was found to be offensive," he said.
A film produced in the United States deemed insulting to Islam sparked world-wide outrage. The U.S. government has denounced the film.
Carney's statement reinforced congressional testimony given early this week by Director of the National Counter-Terrorism Center Matthew Olsen.
U.S. Secretary of State Hillary Clinton said FBI investigators were in Tripoli to join the investigation into the attack.
Military group Ansar al-Sharia was suspected of having a role in the assault. In an interview with the BBC, Ansar al-Sharia commander Mohammed Ali al-Zawawi denied responsibility, however.
Carney said "possibly" elements of al-Qaida in the Islamic Maghreb, the North African branch of al-Qaida, participated in the attack.