QUESTION: Senator, as a retired Navy chief, my thoughts are often with those who serve our country. I know both candidates, both of you, expressed support for Israel.

If, despite your best diplomatic efforts, Iran attacks Israel, would you be willing to commit U.S. troops in support and defense of Israel? Or would you wait on approval from the U.N. Security Council?

MCCAIN: Well, thank you, Terry (ph). And thank you for your service to the country.

I want to say, everything I ever learned about leadership I learned from a chief petty officer. And I thank you, and I thank you, my friend. Thanks for serving.

Let -- let -- let me say that we obviously would not wait for the United Nations Security Council. I think the realities are that both Russia and China would probably pose significant obstacles.

And our challenge right now is the Iranians continue on the path to acquiring nuclear weapons, and it's a great threat. It's not just a threat -- threat to the state of Israel. It's a threat to the stability of the entire Middle East.

If Iran acquires nuclear weapons, all the other countries will acquire them, too. The tensions will be ratcheted up.

What would you do if you were the Israelis and the president of a country says that they are -- they are determined to wipe you off the map, calls your country a stinking corpse?

Now, Sen. Obama without precondition wants to sit down and negotiate with them, without preconditions. That's what he stated, again, a matter of record.

I want to make sure that the Iranians are put enough -- that we put enough pressure on the Iranians by joining with our allies, imposing significant, tough sanctions to modify their behavior. And I think we can do that.

I think, joining with our allies and friends in a league of democracies, that we can effectively abridge their behavior, and hopefully they would abandon this quest that they are on for nuclear weapons.

But, at the end of the day, my friend, I have to tell you again, and you know what it's like to serve, and you know what it's like to sacrifice, but we can never allow a second Holocaust to take place.

BROKAW: Sen. Obama?

OBAMA: Well, Terry, first of all, we honor your service, and we're grateful for it.

We cannot allow Iran to get a nuclear weapon. It would be a game-changer in the region. Not only would it threaten Israel, our strongest ally in the region and one of our strongest allies in the world, but it would also create a possibility of nuclear weapons falling into the hands of terrorists.

And so it's unacceptable. And I will do everything that's required to prevent it.

And we will never take military options off the table. And it is important that we don't provide veto power to the United Nations or anyone else in acting in our interests.

It is important, though, for us to use all the tools at our disposal to prevent the scenario where we've got to make those kinds of choices.

And that's why I have consistently said that, if we can work more effectively with other countries diplomatically to tighten sanctions on Iran, if we can reduce our energy consumption through alternative energy, so that Iran has less money, if we can impose the kinds of sanctions that, say, for example, Iran right now imports gasoline, even though it's an oil-producer, because its oil infrastructure has broken down, if we can prevent them from importing the gasoline that they need and the refined petroleum products, that starts changing their cost-benefit analysis. That starts putting the squeeze on them.

Now, it is true, though, that I believe that we should have direct talks -- not just with our friends, but also with our enemies -- to deliver a tough, direct message to Iran that, if you don't change your behavior, then there will be dire consequences.

If you do change your behavior, then it is possible for you to re-join the community of nations.

Now, it may not work. But one of the things we've learned is, is that when we take that approach, whether it's in North Korea or in Iran, then we have a better chance at better outcomes.

When President Bush decided we're not going to talk to Iran, we're not going to talk to North Korea, you know what happened? Iran went from zero centrifuges to develop nuclear weapons to 4,000. North Korea quadrupled its nuclear capability.

We've got to try to have talks, understanding that we're not taking military options off the table.