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. [my emphasis]

But the fact is, America is the greatest force for good in the history of the world. My friends, we have gone to all four corners of the Earth and shed American blood in defense, usually, of somebody else's freedom and our own.

So we are peacemakers and we're peacekeepers.

... we're a nation of good. [my empzhasis]

Well, you know, Sen. McCain, in the last debate and today, again, suggested that I don't understand. It's true. There are some things I don't understand.

I don't understand how we ended up invading a country that had nothing to do with 9/11, while Osama Bin Laden and Al Qaeda are setting up base camps and safe havens to train terrorists to attack us.

That was Sen. McCain's judgment and it was the wrong judgment.

When Sen. McCain was cheerleading the president to go into Iraq, he suggested it was going to be quick and easy, we'd be greeted as liberators.

That was the wrong judgment, and it's been costly to us.

So one of the difficulties with Iraq is that it has put an enormous strain, first of all, on our troops, obviously, and they have performed heroically and honorably and we owe them an extraordinary debt of gratitude.

But it's also put an enormous strain on our budget. We've spent, so far, close to $700 billion and if we continue on the path that we're on, as Sen. McCain is suggesting, it's going to go well over $1 trillion.

We're spending $10 billion a month in Iraq at a time when the Iraqis have a $79 billion surplus, $79 billion.

And we need that $10 billion a month here in the United States to put people back to work, to do all these wonderful things that Sen. McCain suggested we should be doing, but has not yet explained how he would pay for.

Well, let me just follow up, my friends. If we had done what Sen. Obama wanted done in Iraq, and that was set a date for withdrawal, which Gen. [David] Petraeus, our chief -- chairman of our Joint Chiefs of Staff said would be a very dangerous course to take for America, then we would have had a wider war, we would have been back, Iranian influence would have increased, al Qaeda would have re- established a base.

There was a lot at stake there, my friends. And I can tell you right now that Sen. Obama would have brought our troops home in defeat. I'll bring them home with victory and with honor and that is a fundamental difference.

Katie, it's a terrific question and we have a difficult situation in Pakistan. I believe that part of the reason we have a difficult situation is because we made a bad judgment going into Iraq in the first place when we hadn't finished the job of hunting down bin Laden and crushing al Qaeda.

So what happened was we got distracted, we diverted resources, and ultimately bin Laden escaped, set up base camps in the mountains of Pakistan in the northwest provinces there.

They are now raiding our troops in Afghanistan, destabilizing the situation. They're stronger now than at any time since 2001. And that's why I think it's so important for us to reverse course, because that's the central front on terrorism.

They are plotting to kill Americans right now. As Secretary Gates, the defense secretary, said, the war against terrorism began in that region and that's where it will end. So part of the reason I think it's so important for us to end the war in Iraq is to be able to get more troops into Afghanistan, put more pressure on the Afghan government to do what it needs to do, eliminate some of the drug trafficking that's funding terrorism.

But I do believe that we have to change our policies with Pakistan. We can't coddle, as we did, a dictator, give him billions of dollars and then he's making peace treaties with the Taliban and militants.

What I've said is we're going to encourage democracy in Pakistan, expand our nonmilitary aid to Pakistan so that they have more of a stake in working with us, but insisting that they go after these militants.

And if we have Osama bin Laden in our sights and the Pakistani government is unable or unwilling to take them out, then I think that we have to act and we will take them out. We will kill bin Laden; we will crush Al Qaeda. That has to be our biggest national security priority.

You know, my hero is a guy named Teddy Roosevelt. Teddy Roosevelt used to say walk softly -- talk softly, but carry a big stick. Sen. Obama likes to talk loudly.

In fact, he said he wants to announce that he's going to attack Pakistan. Remarkable.

You know, if you are a country and you're trying to gain the support of another country, then you want to do everything you can that they would act in a cooperative fashion.

When you announce that you're going to launch an attack into another country, it's pretty obvious that you have the effect that it had in Pakistan: It turns public opinion against us.

Now, let me just go back with you very briefly. We drove the Russians out with -- the Afghan freedom fighters drove the Russians out of Afghanistan, and then we made a most serious mistake. We washed our hands of Afghanistan. The Taliban came back in, Al Qaeda, we then had the situation that required us to conduct the Afghan war.

Now, our relations with Pakistan are critical, because the border areas are being used as safe havens by the Taliban and Al Qaeda and other extremist organizations, and we have to get their support.

Now, General Petraeus had a strategy, the same strategy -- very, very different, because of the conditions and the situation -- but the same fundamental strategy that succeeded in Iraq. And that is to get the support of the people.

We need to help the Pakistani government go into Waziristan, where I visited, a very rough country, and -- and get the support of the people, and get them to work with us and turn against the cruel Taliban and others.

And by working and coordinating our efforts together, not threatening to attack them, but working with them, and where necessary use force, but talk softly, but carry a big stick.

We are going to have to make the Iraqi government start taking more responsibility, withdraw our troops in a responsible way over time, because we're going to have to put some additional troops in Afghanistan.

Gen. [David] McKiernan, the commander in Afghanistan right now, is desperate for more help, because our bases and outposts are now targets for more aggressive Afghan -- Taliban offenses.

We're also going to have to work with the Karzai government, and when I met with President Karzai, I was very clear that, "You are going to have to do better by your people in order for us to gain the popular support that's necessary."

I don't think he has to be a dictator. And we want a democracy in Afghanistan. But we have to have a government that is responsive to the Afghan people, and, frankly, it's just not responsive right now.

Brokaw: This requires only a yes or a no. Ronald Reagan famously said that the Soviet Union was the evil empire. Do you think that Russia under Vladimir Putin is an evil empire?

Obama: I think they've engaged in an evil behavior and I think that it is important that we understand they're not the old Soviet Union but they still have nationalist impulses that I think are very dangerous.

Brokaw: Sen. McCain?

McCain: Maybe.

Brokaw: Maybe. [my emphasis]

My friends, we are not going to be able to provide the same benefit for present-day workers that we are going -- that present-day retirees have today. We're going to have to sit down across the table, Republican and Democrat, as we did in 1983 between Ronald Reagan and Tip O'Neill.

I know how to do that. I have a clear record of reaching across the aisle, whether it be Joe Lieberman or Russ Feingold or Ted Kennedy or others. That's my clear record.

There are lots of issues that we are going to be dealing with here tonight. And we have a question from Langdon (ph) in Ballston Spa, New York, and that's about huge unfunded obligations for Social Security, Medicare, and other entitlement programs that will soon eat up all of the revenue that's in place and then go into a deficit position.

Since the rules are pretty loose here, I'm going to add my own to this one. Instead of having a discussion, let me ask you as a coda to that. Would you give Congress a date certain to reform Social Security and Medicare within two years after you take office? Because in a bipartisan way, everyone agrees, that's a big ticking time bomb that will eat us up maybe even more than the mortgage crisis.

Brokaw: I'm just the hired help here, so, I mean...

Obama: You're doing a great job, Tom.

My friends, what we have to do with Medicare is have a commission, have the smartest people in America come together, come up with recommendations, and then, like the base-closing commission idea we had, then we should have Congress vote up or down.

Let's not let them fool with it anymore. There's too much special interests and too many lobbyists working there. So let's have -- and let's have the American people say, "Fix it for us."

So we're going to have to tell the American people that spending is going to have to be cut in America. And I recommend a spending freeze that -- except for defense, Veterans Affairs, and some other vital programs, we'll just have to have across-the-board freeze.

You know, a lot of you remember the tragedy of 9/11 and where you were on that day and, you know, how all of the country was ready to come together and make enormous changes to make us not only safer, but to make us a better country and a more unified country.

And President Bush did some smart things at the outset, but one of the opportunities that was missed was, when he spoke to the American people, he said, "Go out and shop."

That wasn't the kind of call to service that I think the American people were looking for.

And so it's important to understand that the -- I think the American people are hungry for the kind of leadership that is going to tackle these problems not just in government, but outside of government.

And let's take the example of energy, which we already spoke about. There is going to be the need for each and every one of us to start thinking about how we use energy.

I believe in the need for increased oil production. We're going to have to explore new ways to get more oil, and that includes offshore drilling. It includes telling the oil companies, that currently have 68 million acres that they're not using, that either you use them or you lose them.

We're going to have to develop clean coal technology and safe ways to store nuclear energy.

But each and every one of us can start thinking about how can we save energy in our homes, in our buildings. And one of the things I want to do is make sure that we're providing incentives so that you can buy a fuel efficient car that's made right here in the United States of America, not in Japan or South Korea, making sure that you are able to weatherize your home or make your business more fuel efficient.

And that's going to require effort from each and every one of us.

To giving every American a $5,000 refundable tax credit and go out and get the health insurance you want rather than mandates and fines for small businesses, as Sen. Obama's plan calls for. And let's create jobs and let's get our economy going again. And let's not raise anybody's taxes.

So here's what I would do. If you've got health care already, and probably the majority of you do, then you can keep your plan if you are satisfied with it. You can keep your choice of doctor. We're going to work with your employer to lower the cost of your premiums by up to $2,500 a year.

And we're going to do it by investing in prevention. We're going to do it by making sure that we use information technology so that medical records are actually on computers instead of you filling forms out in triplicate when you go to the hospital. That will reduce medical errors and reduce costs.

If you don't have health insurance, you're going to be able to buy the same kind of insurance that Sen. McCain and I enjoy as federal employees. Because there's a huge pool, we can drop the costs. And nobody will be excluded for pre-existing conditions, which is a huge problem.

Now, Sen. McCain has a different kind of approach. He says that he's going to give you a $5,000 tax credit. What he doesn't tell you is that he is going to tax your employer-based health care benefits for the first time ever.

So what one hand giveth, the other hand taketh away. He would also strip away the ability of states to provide some of the regulations on insurance companies to make sure you're not excluded for pre-existing conditions or your mammograms are covered or your maternity is covered. And that is fundamentally the wrong way to go.

In fact, just today business organizations like the United States Chamber of Commerce, which generally are pretty supportive of Republicans, said that this would lead to the unraveling of the employer-based health care system. [my emphasis]

And if you do the math, those people who have employer-based health benefits, if you put the tax on it and you have what's left over and you add $5,000 that you're going to get as a refundable tax credit, do the math, 95 percent of the American people will have increased funds to go out and buy the insurance of their choice and to shop around and to get -- all of those people will be covered except for those who have these gold-plated Cadillac kinds of policies.

But this is another example where I think it is important to look at the record. Sen. McCain and I actually agree on something. He said a while back that the big problem with energy is that for 30 years, politicians in Washington haven't done anything.

What Sen. McCain doesn't mention is he's been there 26 of them. And during that time, he voted 23 times against alternative fuels, 23 times.

So it's easy to talk about this stuff during a campaign, but it's important for us to understand that it requires a sustained effort from the next president.

So what that means is that we can't simply drill our way out of the problem. And we're not going to be able to deal with the climate crisis if our only solution is to use more fossil fuels that create global warming.