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(BEGIN VIDEO CLIP)

MICHAEL BLOOMBERG, MAYOR OF NEW YORK CITY: It was more specific as to target. It was more specific as to timing.

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"FOX NEWS SUNDAY" HOST CHRIS WALLACE: That was New York City Mayor Michael Bloomberg talking about the terror threat this week against that city's subway system. But while local officials beefed up security to protect New Yorkers, they also had some differences with federal authorities about the credibility of that threat.

Here to bring us the latest is New York City Police Commissioner Raymond Kelly, who joins us from Fox News headquarters in New York.

Commissioner Kelly, thanks for finding the time to talk with us today.

NEW YORK CITY POLICE COMMISSIONER RAYMOND KELLY: Good to be with you, Chris.

WALLACE: The terror alert that you received from the federal government -- and let's put it up on the screen, if we can -- specifically warned that a team of terrorist operatives, some of whom may travel to or who may be in the New York City area, may attempt to execute an attack on the New York City subway on or about October 9, 2005.

That, of course, is today, Commissioner Kelly. Are you taking any specific measures to deal with this attack that may happen today?

KELLY: Well, we certainly are, Chris. We've actually been doing that since Thursday evening. We had a little bit more specific information than that warning gives you.

But we've increased our officers in the transit system. We're working with the commuter lines, the Metropolitan Transportation Authority (search), the Port Authority Police (search). We've increased our bag searches. You'll see more dogs in the subway system. We've done quite a bit, and we're continuing to do that until we have a level of comfort that the threat has been reduced.

WALLACE: Let me ask you how long you're going to proceed. When New Yorkers return to work from holiday on Tuesday, will there still be the beefed-up security that they saw on Thursday?

KELLY: Well, let me say this. Operations are going on overseas that we believe will give us a better sense of the credibility of this threat in the short term. So we'll be governed, to a large extent, as to what comes to us from the intelligence community overseas.

WALLACE: And can you give us a sense of this rolling information that you're getting? Because there have been some reports out of Iraq that there was an informant, that they arrested the informant, then he named three people, they arrested them, and that it doesn't seem to have gone any further. You make it sound like the case is still pretty open.

KELLY: Well, there are other aspects to this. I'm a little bit constrained because I am privy to classified information, and I'm not going to get into the details of it, but I think suffice it to say that there are operations that are ongoing. Interrogations are taking place.

There are a few different aspects to this threat, but hopefully we'll have more specific -- or more credible information, I should say, in the near term that will enable us to make a determination as to how much longer we keep this heightened level of security in place.

WALLACE: But you make it sound as if the interrogation and the investigation are still ongoing.

KELLY: That's correct. They are.

WALLACE: How will you end up deciding when it's time that you can safely ease off on this beefed-up security?

KELLY: Well, you know, there are various means that are used. Polygraph machines -- that is, lie detectors -- are used. So we'll see what the determination is based on -- the interrogation processes that are going forward overseas, plus there's investigations that are going on here as well.

WALLACE: As you well know, it's been widely reported that federal officials are downplaying the seriousness of this threat. Let's put up on the screen again, if we can, that homeland security bulletin.

In it, it says DHS -- that's Department of Homeland Security (search) -- and the FBI (search) have doubts about the credibility of the threat based on the information we have to date.

Now, the head of the 9/11 Commission, former New Jersey Governor Kane, says he thinks it's wrong for federal officials to be undercutting local officials like yourself. What do you think about that?

KELLY: Well, we have a responsibility to the 8.1 million people that live in this city. We have 4.7 million transit riders a day here in New York City. We're in a city that's been attacked twice successfully by terrorists, almost 3,000 people killed here four years ago, so we might have a different set of priorities than other folks. We understand that.

We have, you might say, almost different missions. We have to react immediately when we get very specific information. We can't wait for absolute certitude. We did, in my judgment, precisely what we should have done. If we had a similar set of facts coming down the pike, we'd do exactly the same thing. The mayor has said that. We simply have no choice in this matter.

WALLACE: But, Commissioner, doesn't it confuse the public, in this case New Yorkers, when one level of government sends one message and another level of government is saying something very different?

KELLY: Well, it might. But hopefully, New Yorkers have confidence in their local government. I think we put in place a comprehensive counterterrorism program. And again, we simply don't have the ability to wait for absolute certitude here. We've got to take action. We did that.

I believe it gives the riding public a level of comfort when we increase our level of security. New Yorkers are tough people. They know that we're in the crosshairs of terrorists. They want to be told what the facts are.

We told them what the facts were, certainly, as far as the specificity of the threat. Again, we acted appropriately, and as the statement from the secretary of Homeland Security that came out yesterday saying that our response -- I think he said absolutely appropriate.

WALLACE: Commissioner, we're running out of time. I've got a couple of questions I want to ask you. First of all, let's talk about the threat. Do you have any evidence that any of these alleged terrorists have actually made it into this country?

KELLY: We are investigating that matter, as you can well understand. So I can't say that there's specific evidence at this time. But clearly, that's an active part of the investigation.

WALLACE: Are you actually looking for anyone specific in this country at this time?

KELLY: I don't want to get into that level of detail, but that part of the investigation is very active, and we're moving in a lot of different areas in that regard.

WALLACE: You say "very active". There was talk -- they have apparently arrested three of the alleged conspirators in the Baghdad area, and there was talk about a fourth man who might already be here. Are you looking for that fourth man?

KELLY: That's certainly part of the investigation, yes.

WALLACE: Is there a fourth man, and do you know the name?

KELLY: We're trying to make that determination at this time, yes.

WALLACE: And finally, if it turns out, as we all hope, that this turns out to be bad information, that there is no terrorist threat, what have you learned over the last few days about how well prepared New York City is four years after 9/11?

KELLY: I think we're certainly much better prepared than we were four years ago. We get better prepared, really, on a daily basis. We have drills every day where we're refining and maturing our system, so I think we're well prepared.

There are no guarantees, but I think we're doing everything we can reasonable do to protect the City of New York.

WALLACE: Commissioner Kelly, we want to thank you so much for talking with us. And good luck, sir.

KELLY: Good to be with you, Chris.