Hagel believes that the world is moving toward more diffused power structure where the United States no longer remains the single unchallenged superpower. That, combined with America's internal problems and the desire for Americans to end over a decade of war, points to the need for a diplomatic solution in Syria, he said.

"We've got to understand great-power limitations. There are so many uncontrollable variables at play in Syria and the Middle East," Hagel said. "You work through the multilateral institutions that are available, the U.N., the Arab league. The last thing you want is an American-led or Western-led invasion into Syria."

On Iran, Hagel said that polls available at the time showed that the vast majority of both Americans and Israelis didn't think it wise for Israel to attack Iran in the near term. There's plenty more time to seek a diplomatic solution, he said.

"The two options -- attack Iran or live with a nuclear-armed Iran -- may be eventually where we are. But I believe most people in both Israel and the United States think there's a ways to go before we get to those," Hagel said. "I think Obama is handling this exactly the right way. I can understand differences between Obama and the Israeli prime minister, but we have differences with all our allies."

Hagel rejected the notion that Obama has put distance between the United States and Israel or mistreated Israel in any way.

"That's complete nonsense. Anything who knows anything about this knows it's nonsense," he said.