US Secretary of State Hillary Clinton announced Thursday she was setting up an official review of security at a US mission in Libya following a militant attack which killed four Americans.
She unveiled the move just before addressing US lawmakers in closed-door briefings to discuss the US "security posture, before and during the events and the steps we have taken since."
US ambassador to Libya Chris Stevens and three other Americans were killed in the four-hour attack on September 11 on a diplomatic mission to Benghazi, which came amid protests over an anti-Islamic film.
"I will advise Congress... I am launching an accountability review board that will be chaired by ambassador Thomas Pickering," Clinton told reporters, before her meetings.
Under US law, the secretary of state must convene an accountability review board within 60 days of a security incident at a diplomatic mission which involves "serious injury, loss of life, or significant destruction of property," a State Department official said.
Pickering, who will head up the review board, is an 80-year-old retired diplomat who had a four-decade career notably as ambassador to the United Nations from 1989 to 1992, as well as envoy to Israel and Jordan.
The board consists of five members, of which four including the chairman are appointed by Clinton and the fifth by the national director of intelligence.
The official said the review would cover such things as "whether the security systems and security procedures at that mission were adequate," whether they were properly implemented and what kind of intelligence was available.
It will submit its findings and recommendations to Clinton, who will then have 90 days to give a report to Congress on what actions have been taken on each of the recommendations.
Clinton was accompanied by the National Intelligence Director James Clapper, Deputy Defense Secretary Ash Carter, and Sandy Winnefeld, vice chairman of the Joint Chiefs of Staff, as well as FBI and State Department experts.
However, the top US diplomat rejected outright rumors that Stevens had said in the weeks before his death that he was on an Al-Qaeda hit list.
"I have absolutely no information or reason to believe there's any basis for that," she told reporters after hosting a US-Indonesia joint commission.
After the briefings, lawmakers said officials now believed the attack was not a spontaneous assault on the mission.
"They're now saying that it was not a demonstration, this was a pre-planned attack," said Republican Representative Buck McKeon, chairman of the House Armed Services Committee.
Veteran Senator John McCain told reporters there was some evidence of involvement by Al-Qaeda or a radical Islamist group in Benghazi.
And he blasted the administration for its initial assessment, saying "it shows the gizmo level of their knowledge of this fundamental aspect of terror attacks and militant operations."
But Democrat Adam Smith, the ranking member of the House Armed Service Committee, told reporters: "They're still piecing it together, obviously still trying to figure out who perpetrated the attack. It's clearly a terrorist attack, but who exactly perpetrated it is the question."