Two prominent Libyans familiar with the terrorist group insist it was behind the assault that killed U.S. Ambassador Christopher Stevens

Three weeks after the calamitous attack on the U.S. consulate in Benghazi, a former Libyan intelligence chief tells TIME that he is convinced that the assault was a premeditated operation carried out by al-Qaeda’s North African wing — an organization that until now was believed to have a stronger presence elsewhere in the region. “It is not what I think. It is what I know,” insists Rami El-Obeidi, who until late last year was in charge of intelligence for the rebel national transitional government that eventually overthrew Muammar Gaddafi. “It is my very strong belief that this was an operation that was preplanned and that it has been executed by al-Qaeda in the Islamic Maghreb.”

Though weeks have passed, the political ramifications about what went so disastrously wrong in Benghazi on Sept. 11 continue to gather steam in Washington. The attack killed the American ambassador, Christopher Stevens — the first such death of a U.S. envoy in three decades — as well as two Navy SEALs and a fourth American. And although it occurred on the anniversary of the 2001 attacks, when security is typically on high alert, the assault by militants armed with rocket-propelled grenades seemed to catch those inside the consulate totally off guard, leaving them trapped and outgunned in a building with inadequate protection.

U.S. officials at first speculated that the attack had been the result of a protest that spun horribly out of control. On Meet the Press on Sept. 16, U.S. Ambassador to the U.N. Susan Rice said the attack had been “initially a spontaneous reaction” to the riots outside the U.S. embassy in Cairo earlier in the afternoon of Sept. 11, a copy of a protest against a California-made video uploaded to YouTube that denigrated the Prophet Muhammad. Last week Republican Senators criticized Rice over that assessment, which has since been rescinded by U.S. officials. Nevertheless, State Department spokeswoman Victoria Nuland told reporters on Monday that Secretary of State Hillary Clinton believes Rice “has done a superb job.”

Among Libyan intelligence experts, however, the early statements out of Washington seemed confounding, since in their view a terrorist attack had seemed almost foretold — and disconnected from the protests against the YouTube video. “It had absolutely nothing to do with the ridiculous film about the Prophet,” Obeidi tells TIME. Speaking from Benghazi, he says he had in fact been deeply concerned about a possible attack there, where the revolution began last year. “Don’t forget, al-Qaeda had started to operate right from the beginning of the revolution,” he says. “They have been in preparation mode and organized their ranks from the first week of March of 2011 and infiltrated many of the brigades.”

With al-Qaeda’s ranks in place in Libya, Obeidi argues, terrorist operatives waited for the right moment to strike. The signal for action might have come on Sept. 10, when al-Qaeda posted a 42-min. videotaped statement by its leader Ayman al-Zawahiri on jihadi websites, announcing that top al-Qaeda commander Abu Yahya al-Libi, a Libyan, had been killed in a U.S. drone strike in Pakistan three months earlier. Al-Zawahiri called for vengeance, saying, “His blood urges you and incites you to fight and kill the crusaders.”

As soon as the video hit the Internet, an al-Qaeda strike in Libya seemed possible, according to Noman Benotman, the former commander of the Libyan Islamic Fighting Group, which had been an al-Qaeda affiliate until breaking ranks with Osama bin Laden in the 2000s. Speaking to TIME on Tuesday, Benotman said he told a Western terrorism expert — whom he did not name — that “if nothing happens by Sept. 13, we will be very lucky, but the next 48 hours there is a very high possibility.” Benotman, who now runs the antiextremist Quilliam Foundation in London, says he and that expert have since “met and he said, ‘You were right.’”

Drawing the links between the Benghazi attack and the actual structure of al-Qaeda in the Islamic Maghreb, or AQIM, is now a crucial task for U.S. intelligence officials and investigators. Citing security sources in Benghazi, Benotman says that among the 50 or so people arrested after the attack were “Malians and Algerians,” suggesting that the regional terrorist organization was involved. “Without a doubt, there is a connection between AQIM and Libya,” he says. “They have opened channels. They have laid down the infrastructure for future attacks.”

In addition, there have been signs of large quantities of arms being smuggled into and out of Libya in recent months, many of them from the giant arsenals left over from Gaddafi’s dictatorship. In early September, Tunisian officials arrested arms smugglers on its border with Libya. And in late September, Algerian officials arrested several people ferrying massive quantities of weaponry from Libya; they were apparently heading toward Niger and Mali.

With all the pieces in place for an al-Qaeda attack, Obeidi says he and others “expected something on Sept. 11. There was the al-Libi death. And what could be more of a symbolic date than that?”

How U.S. officials were taken by surprise or were left unprepared is part of the controversy now roiling in Washington. Benotman, who meets occasionally with U.S. officials and has become a regular guest at antiterrorism gatherings, says he believes the Administration has lately downplayed the threat of al-Qaeda, “as if it was dead these past 12 months,” in order to highlight its successes in fighting terrorism, including the killing of Osama bin Laden. For that reason, he believes the initial U.S. response about the Benghazi attack “was more of a political response than a fact-based response.”

Obeidi has a simpler explanation for why the U.S. apparently missed the threat of an attack: “There was a massive intelligence failure on behalf of our American friends,” he says, adding, “However, I do believe that the Americans learn very fast from their mistakes.”

Clarification: In an e-mail to TIME, Susan Rice’s spokeswoman, Erin Pelton, said the ambassador’s original assessment of the Benghazi attack being spontaneous was “the best information” the Administration had at the time. Pelton noted that an “FBI investigation would provide the definitive accounting of what transpired in Benghazi.”

Correction: The original version of this story said that GOP Senators called for Rice’s resignation. While several Republican Senators have criticized Rice’s assessment of the incident, only Representative Peter King, a Republican from New York, has demanded her resignation.