Leon Panetta: “I urge you to do whatever you can to try to avoid this threat to our national defense.”

I don’t think there is any question that we are dealing with classified information.

Make no mistake about it, that would be an act of war because it would threaten our national security.

I think the United States ought to be part and parcel of any agreement to be able to provide a security assurance to make sure that Ukraine is protected from the kind of invasion that we've seen from Russia.

The answer is no, not at all. Not in 100 years. These plans that the Pentagon develops, we -- we develop these plans to deal with every potential crisis that's out there.