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Exclusive: Panetta says US can't wait for others to act on Syria

Former Defense Secretary Leon Panetta spoke with NBC's Lester Holt in an exclusive interview about a possible U.S. attack on Syria.

Former Defense Secretary Leon Panetta said Friday "it would be nice" if the U.N. or America's allies took military action against Syria over chemical weapons but that the U.S. can't wait for them.

"When that line has been drawn and action needs to be taken, then the United States ultimately has to do that for the sake of the world and the sake of world peace," Panetta said an exclusive interview with Lester Holt for "NBC Nightly News."

He spoke shortly after Secretary of State John Kerry, in a forceful speech, laid out the case against Syrian President Bashar al-Assad and decried what he said were the deaths of 1,429 people, including 426 children, in last week's mass poisoning in Damascus.

Panetta said the Defense Department presented the White House with scenarios for a strike on Syria months ago.

"The military, what they are good at is spending their time planning for exactly these kinds of very limited attacks," he said. "And mark my words, when they decide to do it — the United States military is the best at doing that kind of effort if we have to."

The "biggest challenge," he said, speaking from the Panetta Institute for Public Policy in Seaside, Calif., would be getting it all done in one shot.

Former Defense Secretary Leon Panetta says the Assad regime was involved in deploying chemical weapons against civilians.  He adds that strikes could deter the Syrian government from continuing assaults against its own people. NBC's Lester Holt reports.

"The key here is to be able to make sure that the targets that we're going after are there, that the intelligence is accurate with regards to where those targets are and that we do an effective job of being able to destroy those targets.

"That's going to be a key. And if for any reason we fail to do that, then we're going to have to go back and make sure we do it."

But, he said, if it succeeds, an attack on Assad's military apparatus "could be the beginning of another chapter in this horrible war."

"It hopefully can set the groundwork to be able to pursue a diplomatic strategy that can ultimately result in a negotiated settlement there that bring the needed peace and stability that Syria absolutely requires and that has Assad step down," Panetta added.

Asked about the American people's ambivalence toward strikes, Panetta said he understood that "people are exhausted by war."

"But at the same time, we continue to have a responsibility to exercise leadership in the world," he said. "It would be nice if the U.N. acted. It would be nice if our allies acted. It would be nice if others were willing to take that action."

In lieu of military action, he called on allies to join the U.S. in diplomatic efforts against Assad.

"I understand in the end that the United States probably is one of the very few countries that militarily has the capability to do what we should do there in terms of a very precise and targeted attack," he added.

More on Syria from NBC News:

Secretary of State John Kerry condemns Syria for mass killing. NBC's Andrea Mitchell reports.