Panetta: Obama has 'responsibility' to 'back up' his word on Syria

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In 2012, Obama said that "a red line for us is we start seeing a whole bunch of chemical weapons moving around or being utilized."

In his interview Friday, Panetta said Obama needed to stand by his proclamation.

“Having drawn a clear red line that Syria should not use chemical weapons, same kind of red line that we’ve drawn on Iran, with regards to the use of nuclear weapons, it is absolutely important to our national security interest that we back up that word and take action when that line has been violated," Panetta said.

He added that although he recognized "that the American people are exhausted by war," the evidence that the Assad regime had used chemical weapons was "pretty clear."

"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 of others were willing to take that action. But when that line has been drawn and action needs to be taken, then the U.S. ultimately has to do that for the sake of the world and for the sake of world peace.”

Earlier Friday, Obama said that he had not definitively determined to use military force, but was weighing a "narrow, limited" strike.

Obama himself said he understood that many nations were "war wary," and said he "very much appreciate[d]" their caution himself.

But, he contended, "it’s important for us to recognize that when over a thousand people are killed, including hundreds of innocent children, through the use of a weapon that 98 or 99 percent of humanity says should not be used even in war, and there is no action, then we’re sending a signal."