BRIAN ROSS, ABC CHIEF INVESTIGATIVE CORRESPONDENT: After more than six years of trying, the United States still does not have a reliable way to spot nuclear material that terrorists might smuggle into the country, much as ABC News twice did in demonstrations without being caught.
And after six years of trying, the United States has yet to capture the man who says it is his religious duty to get nuclear weapons: Osama bin Laden.
And in the last 18 months, U.S. officials say his Al Qaida has regrouped using safe havens along the Pakistani border to train and dispatch hundreds of new recruits.
ROSS: And just as troubling, amidst all the turmoil in Pakistan, the influence of bin Laden continues to grow there, a country with many nuclear weapons.
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GIBSON: Brian Ross there.
Well, Osama bin Laden, as he pointed out, has said it is his duty to try to get nuclear weapons. Al Qaida has been reconstituted and re-energized in the western part of Pakistan.
And so my general question is, how aggressively would you go after Al Qaida leadership there?
And let me start with you, Senator Obama, because it was you who said in your foreign policy speech that you would go into western Pakistan if you had actionable intelligence to go after it, whether or not the Pakistani government agreed. Do you stand by that?
OBAMA: I absolutely do stand by it, Charlie. What I said was that we should do everything in our power to push and cooperate with the Pakistani government in taking on Al Qaida, which is now based in northwest Pakistan. And what we know from our national intelligence estimates is that Al Qaida is stronger now than at any time since 2001.
OBAMA: And so, back in August, I said we should work with the Pakistani government, first of all to encourage democracy in Pakistan so you've got a legitimate government that we're working with, and secondly that we have to press them to do more to take on Al Qaida in their territory.
What I said was, if they could not or would not do so, and we had actionable intelligence, then I would strike.
And I should add that Lee Hamilton and Tom Keaton, the heads of the 9/11 Commission, a few months later wrote an editorial saying the exact same thing.
I think it's indisputable that that should be our course.
Let me just add one thing, though. On the broader issue of nuclear proliferation, this is something that I've worked on since I've been in the Senate. I worked with Richard Lugar, then the Republican head of the Senate Foreign Relations Committee, to pass the next stage of what was Nunn-Lugar so that we would have improved interdiction of potentially nuclear materials.
OBAMA: And it is important for us to rebuild a nuclear nonproliferation strategy, something that this administration, frankly, has ignored, and has made us less safe as a consequence.
It would not cost us that much, for example, and would take about four years for us to lock down the loose nuclear weapons that are still floating out there, and we have not done the job.
GIBSON: I'm going to go the others in a moment, but what you just outlined is essentially the Bush doctrine. We can attack if we want to, no matter the sovereignty of the Pakistanis.
OBAMA: No, that is not the same thing, because here we have a situation where Al Qaida, a sworn enemy of the United States, that killed 3,000 Americans and is currently plotting to do the same, is in the territory of Pakistan. We know that.