‘A constant cat and mouse game’

BRIAN WILLIAMS, anchor: Also joining us from our Washington bureau tonight, Michael Leiter , who served as head of the National Counterterrorism Center under both Presidents Bush and Obama , and was, in fact, in the White House Situation Room a year ago during that raid that killed bin Laden . He is, these days, a national security analyst for us here at NBC News . And, Michael , you have to admit the talk has been about how much al-Qaeda has been degraded. So beyond the fact that this was successful, it was intercepted, what do you take from this regarding their strength? What should we take from this?

Mr. MICHAEL LEITER (NBC News National Security Analyst): Brian , I think this really shows that al-Qaeda in Yemen , al-Qaeda in the Arabian Peninsula , as it is known in government circles, remains a very potent threat. As Pete noted: 2009 , Abdulmutallab ; 2010 , the cartridge bombs. The growing instability in Yemen , especially in the south of the country, has left Yemen open as a safe haven for terrorism, and this is a group that despite how they've been wounded, is still very, very much committed to killing Americans.

WILLIAMS: Are you -- what do you take away from this, at least the attempt at technology and again another attempt to evade the traditional forms of detection?

Mr. LEITER: This is a constant cat and mouse game between government intelligence organizations and terrorists. Al-Qaeda knows that we've obviously changed our means of detecting bombs through the advanced screening we have in US airports, but they are looking for weaknesses at every turn. And it's those weaknesses that they are seeking to exploit now. And I hate to say, but I don't think this will be the last. They will learn from this disruption and they will attempt to change their means so the next time it can get through. So we're going to have to continue to be on top of them both offensively and defensively.

WILLIAMS: And final quick question, for those of us who fly, we saw the liquid ban after one attempt. We saw other security measures after the so-called underwear bomb attempt. Do you think we will see evidence at an airport near us in the future that comes out of this intercept today?

Mr. LEITER: I think it will accelerate the advanced screening technology that has been coming out especially over the past two years, and it may well lead to even more stringent screening overseas because at least, at this point, most of these threats and attacks are coming from overseas. So I think on the international landscape we will probably see even tighter cooperation and more stringent security measures.

WILLIAMS: Michael Leiter , who most recently was head of the National Counterterrorism Center , thank you very much for being with us from Washington tonight.