The State Department denied Tuesday it ever concluded that the deadly consulate attack Sept. 11 in Libya was an unplanned outburst prompted by an anti-Islam movie, despite public statements early on by some in the Obama administration suggesting that was the case.

Sen. Bob Corker, R-Tenn., reacting Wednesday to the latest claims, said he's just "at a loss" for why administration officials ever tried to connect the attack to the film in the first place.

"From the very beginning, everyone knew this was a terrorist attack. I mean, there's no question, and that's why this has been totally bizarre," said Corker, who recently returned from Libya.

The Obama administration used the film explanation for more than a week after assailants killed the U.S. ambassador to Libya and three other Americans. Most notably, the U.S. ambassador to the United Nations, Susan Rice, said in several TV interviews five days after the attack that it appeared to be "spontaneous" violence spinning out of protests of the film.

State Department spokeswoman Victoria Nuland backed up Rice's statements in a press briefing a day later: "I would simply say that ... the comments that Ambassador Rice made accurately reflect our government's initial assessment."

And White House Press Secretary Jay Carney, as late as a week after the attack, said that based on initial information, "we saw no evidence to back up claims by others that this was a preplanned or premeditated attack."

Carney then went on to suggest again the violence was related to the film: "Based on the information that we have now, it was -- there was a reaction to the video -- there was protests in Cairo, then followed by protests elsewhere, including Benghazi, and that was what led to the original unrest."

The new comments from the State Department further highlight the disconnect in the attack's aftermath between what administration officials were saying publicly and what intelligence officials suspected early on -- that the attack was an act of terrorism, more coordinated than a protest that got out of hand.

New documents further suggest internal disagreement over appropriate levels of security before the attack, which occurred on the 11th anniversary of the Sept. 11 terror attacks on the U.S.

Briefing reporters ahead of a hotly anticipated congressional hearing Wednesday, State Department officials provided their most detailed rundown of how a peaceful day in Benghazi devolved into a sustained attack that involved multiple groups of men armed with weapons such as machine guns, rocket-propelled grenades and mortars over an expanse of more than a mile.

But asked about the administration's initial -- and since retracted -- explanation linking the violence to protests over an anti-Muslim video circulating on the Internet, one official said, "That was not our conclusion." He called it a question for "others" to answer, without specifying. The officials spoke on condition of anonymity because they weren't authorized to speak publicly on the matter, and provided no evidence that might suggest a case of spontaneous violence or angry protests that went too far.

The attack has become a major issue in the presidential campaign, featuring prominently in Republican candidate Mitt Romney's latest foreign policy address on Monday. He called it an example of President Obama's weakness in foreign policy matters, noting: "As the administration has finally conceded, these attacks were the deliberate work of terrorists."

The administration counters that it has provided its best intelligence on the attack, and that it refined its explanation as more information came to light. But five days after the attack, Ambassador Rice gave a series of interviews saying the administration believed the violence was unplanned and that extremists with heavier weapons "hijacked" the protest and turned it into an outright attack.

She has since denied trying to mislead Congress, and a concurrent CIA memo that was obtained by The Associated Press cited intelligence suggesting the demonstrations in Benghazi "were spontaneously inspired by the protests at the U.S. Embassy in Cairo" and "evolved into a direct assault" on the diplomatic posts by "extremists."

Alongside defining the nature of the Benghazi attack, Congress is looking into whether adequate security was in place.

According to an email obtained Tuesday by Fox News and other news organizations, the top State Department security official in Libya told a congressional investigator that he had argued unsuccessfully for more security in the weeks before Ambassador Chris Stevens, a State Department computer specialist and two former Navy SEALs were killed. But department officials instead wanted to "normalize operations and reduce security resources," he wrote.

Eric Nordstrom, who was the regional security officer in Libya, also referenced a State Department document detailing 230 security incidents in Libya between June 2011 and July 2012 that demonstrated the danger there to Americans.

Nordstrom is among the witnesses set to testify Wednesday before the House Oversight and Government Reform Committee. According to the panel's chairman, Rep. Darrell Issa, R-Calif., and the head of a subcommittee, Rep. Jason Chaffetz, R-Utah, the State Department refused repeated requests to provide more security for U.S. diplomats in Libya.

"You will note that there were a number of incidents that targeted diplomatic missions and underscored the GoL's (government of Libya) inability to secure and protect diplomatic missions," Nordstrom's email stated.

"This was a significant part of (the diplomatic) post's and my argument for maintaining continued DS (diplomatic security) and DOD (Department of Defense) security assets into Sept/Oct. 2012; the GoL was overwhelmed and could not guarantee our protection.

"Sadly, that point was reaffirmed on Sept. 11, 2012, in Benghazi," he added.

Nordstrom said the incidents demonstrated that security in Libya was fragile and could degrade quickly. He added that Libya was "certainly not an environment where (the diplomatic) post would be directed to `normalize' operations and reduce security resources in accordance with an artificial time table."

Nordstrom also said diplomats in Libya were told not to request an extension of a 16-member special operations military team that left in August, according to an official of the Oversight panel. The official was not authorized to discuss the matter publicly and thus spoke only on the condition of anonymity.

The State Department has said it never received a request to extend the military team beyond August, and added that its members were replaced with a security team that had the same skills.

Democrats on the Oversight committee were sharply critical of Issa, the chairman, calling his investigation "extremely partisan."

"The chairman and his staff failed to consult with Democratic members prior to issuing public letters with unverified allegations, concealed witnesses and refused to make one hearing witness available to Democratic staff, withheld documents obtained by the committee during the investigation, and effectively excluded Democratic committee members from joining a poorly-planned congressional delegation to Libya," a Democratic memo said.

It said in the previous two years, House Republicans voted to cut the Obama administration's requests for embassy security by some $459 million.

The Democratic memo said Nordstrom told committee investigators that he sent two cables to State Department headquarters in March and July 2012 requesting additional diplomatic security agents for Benghazi, but that he received no responses.

He stated that Charlene Lamb, the deputy assistant secretary for international programs, wanted to keep the number of U.S. security personnel in Benghazi artificially low and that Lamb believed the Benghazi facilities did not need any diplomatic security special agents because there was a residential safe haven to fall back to in an emergency.

Issa had a phone conversation Monday with Secretary of State Hillary Rodham Clinton about the committee's investigation.

The FBI is still investigating the attack. Clinton also has named a State Department review panel to look into the security arrangements in Libya.

The Associated Press contributed to this report.