Intelligence officials have disclosed a new detailed timeline of the attack on the American consulate in Benghazi, acknowledging the CIA played a greater role in responding to the attack than has previously been disclosed. A senior U.S. intelligence official also insisted that the CIA security team that initially responded to the attack was not given orders "to stand down in providing support," as had been suggested in media reports.

The timeline provided by a senior U.S. intelligence official gives the first precise account of how CIA security teams provided the first response to the Sept. 11 attack on the diplomatic mission in Benghazi, which killed four Americans, including Ambassador Chris Stevens.

The attack has become a political hot potato in the presidential campaign, with conservatives accusing the administration of not being transparent. The State Department has previously released a detailed account of the night's events, but did not acknowledge a CIA role in the response. The timeline given by a senior Intelligence official confirms that the facility previously described by the State Department as an annex, was in fact, a facility housing CIA security officers. It does not provide any additional details on the current intelligence assessment that the attack was an opportunistic result of earlier protests that day outside the U.S. embassy in Cairo over an anti-Muslim movie.

The official says there was "no second guessing" of those on the ground in Libya by senior officials either in Libya or Washington.

"There were no orders to anybody to stand down in providing support," said the official. The official's comments appeared to be a direct rebuttal of a Fox News report that CIA teams on the ground had been told by superior officers to "stand down" from providing security support to the consulate.

According to the official, upon learning of the attack at the consulate, the security team at the annex responded "as quickly and effectively as possible." The official described how the security team tried to rally additional support from local Libyan forces and heavier weapons, but that when that could not be accomplished "within minutes" they moved out to the compound. The official called the security team "genuine heroes" who risked their lives to save those at the compound.

According to the new timeline the annex received a call at 9:40 p.m. local time that the consulate was coming under attack. A team of six CIA security operatives left the annex for the mission within 25 minutes of that call.

Over the next 25 minutes the security team approached the compound and attempted to secure heavy weapons. They encountered heavy enemy fire when they entered the consulate compound to locate Stevens and the other Americans who were there at the time of the attack.

At 11:11 p.m., an unarmed U.S. military surveillance drone arrived over the compound. U.S. officials have told ABC News that the drone had been redirected to Benghazi from an ongoing mission elsewhere in Libya.

By 11:30pm, all of the Americans, with the exception of the missing Stevens, had left the compound in vehicles that immediately came under fire.

The annex itself came under sporadic small arms and RPG fire for the next 90 minutes before the attackers eventually dispersed.

At around 1 a.m. an additional CIA team of about six security officers from the embassy in Tripoli had arrived at Benghazi. U.S. officials have acknowledged that the embassy in Tripoli had chartered an aircraft to take the team to Benghazi. The official disclosed the new detail that two U.S. military officers were part of the team that flew in from Tripoli.

Upon learning that the situation at the annex had calmed down, the team that came in from Tripoli initially wanted to focus their attention on locating Stevens, who had been taken to a local hospital.

When the team finally managed to secure transportation and an armed escort into Benghazi, they learned that Stevens "was almost certainly dead and that the security situation at the hospital was uncertain." At that point they headed to the annex to help evacuate the Americans located there .

They arrived at the annex at 5:15 a.m., just before mortar rounds begin to hit the complex. The attack killed two security officers, Glen Doherty and Tyrone Woods, who were located on the annex's roof. Doherty had been part of the security team that had flown in from Tripoli. The new attack on the annex lasted only 11 minutes.

Less than an hour later everyone at the annex was evacuated with the help of "a heavily armed Libyan military unit. "