In the short term, we're faced with very, very serious threats about the possibility of these nuclear weapons getting in the hands of a terrorist group or somebody who wants to attack the United States of America.
The first thing is we have to immediately find out who's responsible and go after them. And that is the responsibility of the president of the United States.
Because if someone has attacked us with a nuclear weapon, it means they have nuclear technology, it means they could have gotten another nuclear weapon into the United States that we're unaware of. We have to find these people immediately and use every tool available to us to stop them.
EDWARDS: Secondly, it is the responsibility of the United States -- and by the way, what I'm about to say doesn't just apply to a nuclear attack. It applies to this crisis that exists in Pakistan right now with the assassination of Benazir Bhutto.
It is the responsibility of the president in times like this to be a force for strength, principled strength, but also calmness.
It is enormously important for the president of the United States not to take -- to react and to react strongly, but to do it in a way that is calming for the American people and calming for the world.
Because it would be an enormous mistake for the president of the United States to take a terrible, dangerous situation where millions of Americans or thousands of Americans could have lost their lives, and to ratchet up the rhetoric and make it worse than it already is.
GIBSON: Let me come to the two Sam Nunn questions to you, Senator.
OBAMA: Well, as I said, I've already been working on this. And I think this is the most significant foreign policy issue that we confront.
We would obviously have to retaliate against anybody who struck American soil, whether it was nuclear or not. It would be a much more profound issue if it were nuclear weapons.
That's why it's so important for us to rebuild the Nuclear Non- Proliferation Treaty that has fallen apart under this administration.
We have not made a commitment to work with the Russians to reduce our own nuclear stockpiles. That has weakened our capacity to pressure other countries to give up nuclear technology. We have not locked down the loose nuclear weapons that are out there right now.
These are all things that we should be taking leadership on. And part of what we need to do in changing our foreign policy is not just end the war in Iraq; we have to change the mindset that ignores long- term threats and engages in the sorts of actions that are not making us safe over the long term.
GIBSON: And I know, Senator Clinton, you've worked on this, as well.
CLINTON: Yes, I have.
GIBSON: But in terms of retaliation, this is not likely going to be a state that sets off a nuclear attack (inaudible), it's going to be a stateless group.
CLINTON: Well, the first part of your question was, what would we wish we had done. And I have worked on this in past legislation to move in the direction that I think we should go to have a very high level of commitment from the White House, including a person responsible in our government for marshaling our resources against the proliferation of nuclear weapons.