The former director of the CIA has told a private congressional hearing he believed all along that the attack on a US consulate in Libya was a terrorist strike.
United States ambassador Christopher Stevens and three colleagues were killed in the violence in Benghazi on 11 September this year.
General David Petraeus appeared at the House Intelligence Committee on Friday and was then due to give evidence to the Senate Intelligence Committee, both in closed session.
The testimony on Benghazi comes a week after the general quit over an affair, the BBC reports.
Republicans have criticised the White House over the Benghazi attack, saying that the administration misled the public.
General Petraeus has said he left his CIA post only because of his extramarital affair with biographer Paula Broadwell, not because of the agency's handling of the attack.
The general told the committee that the CIA was aware the attack was planned by terrorists from an early stage, New York Congressman Peter King told reporters after the first session.
However, Mr King said the general's evidence on Friday conflicted with what he said at a hearing on 14 September.
Mr King said he had a "very different recollection" of the earlier hearing, at which lawmakers had been told the attack grew out of spontaneous protests over an anti-Islamic film.
He added that despite General Petraeus' testimony on Friday, it was still not clear who approved the message that the attack was linked to the protests.
The retired four-star general, one of the most prominent US military figures of the post-9/11 years, travelled to Libya in September to investigate what happened in Benghazi.
On Thursday, the CIA launched an investigation into the conduct of General Petraeus.
His former mistress Paula Broadwell, 40, was found to have classified information, but both she and General Petraeus deny it came from him.
A CIA spokesman said the inquiry by the agency's inspector general would see if there were any lessons to be learned from the general's conduct.
The scandal was discovered when FBI officials looked into harassing emails, allegedly from Mrs Broadwell, that were sent to a Florida socialite who is a family friend of the Petraeuses, the BBC reports.
The inquiry has also ensnared the US and Nato commander in Afghanistan, General John Allen.
He is under investigation for sending what officials describe as "flirtatious" emails to Tampa socialite Jill Kelley.
Adultery is illegal under military law, but General Allen denies wrongdoing.