This is a partial transcript of "The Big Story With John Gibson," April 12, 2006, that has been edited for clarity.

JOHN GIBSON, HOST: So how should the U.S. deal with Iran's defiant regime? Let's ask former Secretary of State Lawrence Eagleburger, who served under the first President Bush.

Can the U.S. afford to allow Tehran to proceed and build a bomb?

LAWRENCE EAGLEBURGER, FORMER SECRETARY OF STATE: No, I do not believe we can. That does not mean that we will not let it happen, but if we do it will be a historic mistake on our part. You have to hope that it will not just be the United States, but that some of our so strenuously strong allies would join us in this issue.

But in the end — and I think we still have some time. That's not the issue. But I think if we don't in the end bring this to a halt we will deeply regret it no more than a generation from now.

GIBSON: Mr. Eagleburger, what is the time frame? I've read everything from a year to 10 years.

EAGLEBURGER: The last I knew — and I'm not the expert — but I heard today that the real estimate in terms of where the Iranians now are and how long it would take, that it would probably take them at least three years. I would guess five. So I think again before they have a bomb is some years ahead, but the fact that they have begun to deal with the uranium the way they have, it seems to be once you've past that stage, then it only becomes a question of time of building, getting enough of this uranium so that you can put a bomb together.

So I think if they are telling the truth when they claim this, I think they have gone past an important stage. If they are lying to us, that doesn't mean that the intention isn't there and that they'll keep trying.

GIBSON: All right. Can the United States take military action? Can we bomb something to stop them?

EAGLEBURGER: If we have to. We're not there yet. And I think given the reluctance of some of the other members of the U.N. such as Russia and China, I have to tell you I think the president will be hard pressed to try to do very much along the military line for some period of time.

I personally believe in the end if sanctions and so forth don't work and if we are intent on not letting them build the bomb, that in fact we are going to have to resort to military activity. And I'm not at all sure that it can be directed simply at the facilities where they are trying to make the bomb. I'm not sure we know where all of them are.

So I think it could mean that we have go at the Iranians in terms of some other facilities of theirs as well. But, again, that is some way down the road and it will take a lot of courage to do it, particularly if we can't get anybody else in the world to join us. But in the end, if we don't do it, we will wish we had.

GIBSON: Is this decision going to have to be made in the administration of George W. Bush?

EAGLEBURGER: A very good question. If he could put it off I suppose he would probably do so. But my own view of it is that it has to be made in this administration, even though it may be toward the end of the administration. If we wait for the next administration, I think it's probably waiting too long.

But I can't — you know, nobody could tell you. You say that the president with, let's say, six months left in his term is going to take that situation. So it may well be forced into the next administration.

GIBSON: If we let them have a bomb, will they use it on us?

EAGLEBURGER: If we let them have a bomb, they may never use it. First of all, if they have one before long, they have five or six or whatever. But they may never use it. But the fact that it is there, it is hanging over our heads, totally changes the perspective of how the U.S. deals with the world in general and countries like Iran in particular where now Iran can't really threaten us in any meaningful way.

They can threaten our neighbors, but if they have a few of these bombs and were to suggest, for example, that they're going to put one in the hold of a ship and put it in New York Harbor, if you are the president, you have a much more complicated situation to try to sort your way through.

GIBSON: Former Secretary of State Lawrence Eagleburger, thanks very much.

EAGLEBURGER: My pleasure.

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