Former CIA director David Petraeus told US lawmakers during private hearings he believed all along that the September 11 attack on the US consulate in Libya was a terrorist strike, even though the Obama administration initially described it as protests against an anti-Muslim video.
Questions persist over what the administration knew immediately after the Benghazi attack killed the US ambassador and three other Americans and why its first public statements did not match intelligence agencies' assessments.
The issue has threatened to affect the search for a new secretary of state once Hillary Clinton steps down.
Petraeus addressed intelligence committees in his first Capitol Hill testimony since resigning a week ago over an extramarital affair with his biographer, Paula Broadwell.
The retired four-star general, once the top commander in Iraq and in Afghanistan, said he did not know who removed the reference to terrorism from the CIA's original draft of talking points on the Libya attack, Congressman Peter King said.
Petraeus said references to militant groups Ansar al-Shariah and al-Qa'ida in the Islamic Maghreb were replaced with the word 'extremist' in the final draft, a congressional staffer said.
"The reference to al-Qa'ida was taken out somewhere along the line by someone outside the intelligence community," King said. "We need to find out who did it and why."
Democrats said Petraeus made it clear the change was not made for political reasons.
"The general was adamant there was no politicisation of the process, no White House interference or agenda," said Congressman Adam Schiff.
But Republicans were still critical. Senator Marco Rubio said Petraeus's testimony showed that "clearly the security measures were inadequate despite an overwhelming and growing amount of information that showed the area in Benghazi was dangerous".
King said that, to this day, it is still not clear how the final talking points emerged that were used by UN Ambassador Susan Rice five days after the attack in a series of interviews.