(CBS NEWS) -- Amid protracted Republican criticism of the U.S. response to the September 11 attacks in Benghazi, Libya, Defense Secretary Leon Panetta this morning continued to stand up for the Obama administration's actions surrounding the violence, arguing in a Senate Armed Services Committee hearing that while the U.S. lacked sufficient advance intelligence to anticipate the attacks, we did "everything we could" to save American lives once they had begun.

Panetta, who is finishing out his tenure as the president's top Pentagon official, allowed that extensive steps can and are being taken to prevent similar attacks in the future, and he outlined some of the actions he and other top defense officials have already authorized to that end.

But, like former Secretary of State Hillary Clinton last month, Panetta emphasized the sheer number of security threats faced by U.S. diplomats abroad in the months leading up to the Benghazi attacks, pointing out that Benghazi was one of "almost 300 areas of concern" to the National Counterterrorism Center (NCTC).

"The NCTC, in the six months prior to that attack, identified some 281 threats to U.S. diplomats, diplomatic facilities, embassies, ambassadors and consulates worldwide -- and obviously Benghazi was one of those almost 300 areas of concern," he said.

On September 11, he said he and Gen. Martin Dempsey, the chairman of the Joint Chiefs of Staff, "received a number of reports of possible threats to U.S. facilities, including those in Cairo, Egypt."

"But there were no reports of imminent threats to U.S. personnel or facilities in Benghazi," he said. "Unfortunately, there was no specific intelligence or indications of an imminent attack on that - U.S. facilities in Benghazi. And frankly without an adequate warning, there was not enough time given the speed of the attack for armed military assets to respond."

Barring prior intelligence of the attacks, Panetta argued, the U.S. defense forces could only respond to those which had already begun - and he defended that response as timely and appropriate.

"Despite the uncertainty at the time, the Department of Defense and the rest of the United States government spared no effort to do everything we could to try to save American lives," he said. "The bottom line is this, that we were not dealing with a prolonged or continuous assault, which could have been brought to an end by a U.S. military response, very simply, although we had forces deployed to the region. Time, distance, the lack of an adequate warning, events that moved very quickly on the ground prevented a more immediate response."

While Panetta defended the Obama administration's response from a defense standpoint, the committee's top Republican, Sen. Jim Inhofe, R-Okla., said he was more concerned with the government "cover-up" that he argued followed the attacks.

"We sit around all day long and talk about the resources that we should have and don't have, not just here and not just in this part of the world, but all over the world and... that's fine," he said. "I think we all understand that. But that's not the big problem here, and the big problem here is the cover-up that nobody talks about, and that's the tragedy."

Beginning his questioning later in the hearing, Inhofe added: "I think the skunk is about to arrive at the picnic."

The committee's chairman, Sen. Carl Levin, D-Mich., meanwhile, focused on the looming sequestration cuts that threaten to cut more than half a trillion dollars of defense spending - a topic about which Panetta has spoken vocally in recent weeks.

Panetta, in his opening remarks, referred to the sequester cuts as "one of the greatest security risks we're now facing as a nation," and which he argued "could prompt the most significant readiness - military readiness crisis in more than a decade."

"We have a responsibility -- and I take that responsibility seriously -- to do everything we can to protect our citizens," he said. "That responsibility, however, rests with both the executive branch and the Congress. If we work together, we can keep our Americans safe."