Attack on U.S. Consulate in Libya determined to be terrorism tied to al-Qaeda U.S. intelligence officials said the composition of the militant forces involved in the assault has become clearer over the past week and that analysts now think that two or three fighters affiliated with al-Qaeda in the Islamic Maghreb were involved. "There are people who at least have some association with AQIM," said a senior U.S. intelligence official who added that "it's not so direct that you would say AQIM as an organization planned and carried this out." Instead, U.S. officials said a ­lesser-known Islamist group, ­Ansar al-Sharia, played a much larger role in sending fighters and providing weapons for the attack, which killed the U.S. ambassador and three other Americans. U.S. officials have previously cited suspicion of al-Qaeda connections to the attack. The intelligence picture assembled so far indicates that militants had been preparing an assault on the U.S. compound in Benghazi for weeks but were so disorganized that, after the battle started, they had to send fighters to retrieve heavier weapons. U.S. intelligence officials said they think the attack was not timed to coincide with the Sept. 11, 2001, anniversary. Instead, the officials said, the assault was set in motion after protesters scaled the walls of the U.S. Embassy in Cairo as part of a protest of an amateur anti-Islamic YouTube video. "There's never been any intelligence, nor any I'm aware of now, that indicated this was a plot planned months in advance to get turned on on 9/11," said an Obama administration official. The emerging scenario, the official said, "is that extremists in the region had cased out and hoped to target U.S. facilities in Benghazi for some time. When they saw what was happening in Cairo, that influenced their timing. The officials spoke on the condition of anonymity to describe the preliminary assessments of analysts involved in an ongoing investigation of the Benghazi attack that involves the FBI, the CIA and other agencies. The question of whether the attack was a pre-planned act of terrorism has become entangled in the politics of the ongoing presidential campaign. Republicans have accused the administration of being reluctant to attribute the Benghazi assault to terrorism, suggesting it could make Obama vulnerable on a perceived foreign policy strength - the success of the campaign against al-Qaeda - and raise questions about his handling of the rise of Islamist factions in the aftermath of the Arab Spring. The State Department said Thursday that it was pulling more American staff from the U.S. Embassy in Tripoli out of concern for their safety. A State Department official described the reduction as temporary and said the embassy was not being closed. The State Department would not say how many people are leaving or how many will stay.