Just days before the presidential election, U.S. officials are striking back at allegations they failed to respond quickly or efficiently against the deadly attack on the U.S. Consulate in Benghazi, Libya, detailing for the first time a broad CIA rescue effort.

Senior U.S. intelligence officials said Thursday that CIA security officers went to the aid of State Department staff less than 25 minutes after they got the first call for help from the consulate, which was less than a mile (1.6 km) from a CIA annex.

The detailed timeline provides the first in-depth look at how deeply the CIA was involved in the rescue attempt, and it comes amid persistent questions about whether the Obama administration responded as quickly and effectively as it could to the siege.

The attack on the 11th anniversary of Sept. 11 by what is now suspected to be a group of al-Qaida-linked militants killed U.S. Ambassador Chris Stevens and three other Americans. Two of the four who were killed, ex-Navy commandos Tyrone Woods and Glenn Doherty, had been identified as State Department contractors, but were actually CIA security officers who responded from the annex.

U.S. officials described the timeline in a clear effort to rebut recent news reports that said the CIA told its personnel to "stand down" rather than go to the consulate to help repel the attackers. Fox News reported that when CIA officers at the annex called higher-ups to tell them the consulate was under fire, they were twice told to "stand down." The CIA publicly denied the report.

The intelligence officials told reporters Thursday that when the CIA annex received a call about the assault, about a half dozen members of a CIA security team tried to get heavy weapons and other assistance from the Libyans. But when the Libyans failed to respond, the security team, which routinely carries small arms, went ahead with the rescue attempt. At no point was the team told to wait, the officials said.

Instead, they said the often outmanned and outgunned team members made all the key decisions on the ground, with no second-guessing from senior officials monitoring the situation from afar.

The officials insisted on anonymity to discuss a CIA operation, as they routinely do. The anonymity was a condition of discussion even on a topic that has become highly politicized days before the presidential election.

The consulate attack has become a political issue in Washington, with Republicans questioning the security at the consulate, the intelligence on militant groups in North Africa and the Obama administration's response in the days after the attack. Republicans also have questioned whether enough military and other support was requested and received. And presidential candidate Mitt Romney has used the attack as a sign of what he says is President Barack Obama's weak leadership overseas.