Updated

This is a rush transcript from "On the Record," January 11, 2012. This copy may not be in its final form and may be updated.

GRETA VAN SUSTEREN, FOX NEWS HOST: One of the GOP candidates is getting a brand-new endorsement right now, and it is a big one! Former U.N. ambassador John Bolton is here to announce his pick. Ambassador Bolton, I'm not going to steal your thunder. I know who it is. But tell the viewers, who are you endorsing, sir?

JOHN BOLTON, FOX NEWS CONTRIBUTOR/FORMER U.S. AMBASSADOR TO U.N.: Well, I'm going to support Mitt Romney. I've thought about this very hard. This is extraordinarily important decision for the Republican Party. I believe it is absolutely critical to defeat Barack Obama in November. I think our country would be in dire straits domestically and internationally if he gets another four years. And I think Governor Romney is the person who can best lead the party, best articulate our conservative principles, and is most likely to beat Barack Obama.

VAN SUSTEREN: All right. Now, Speaker Gingrich and Senator Santorum both describe him as a moderate. And they point to many of the things that happened in the state of Massachusetts. Do you disagree with them that -- in their critique -- in their critique of his policies as being moderate in many instances?

BOLTON: Well, let me put it this way. Looking at the whole range of prospective candidates, there was only one prospective candidate who met my test as the ideal conservative, but he decided not to run.

VAN SUSTEREN: Who's that?

BOLTON: So faced with looking at everyone else...

VAN SUSTEREN: I guess -- is that you?

BOLTON: I guess -- I guess he's sitting here! So faced with everybody else, I followed the William F. Buckley, Jr., test, which is to find the most conservative candidate who is capable of getting elected. There are obviously two variables there. But you know, in the words of the old song, "Give Me That Old-Time Religion," Romney's conservative enough for me, and I think he's the one most likely to get elected, and I think that's critical.

VAN SUSTEREN: You know, I always sort of -- I'm guilty of typecasting people, and I suppose others are. I would think that the most important criteria to you would be foreign policy, obviously. And I'm curious how you think a President Romney foreign policy would differ in any way from a President Gingrich or a President Santorum in any way?

BOLTON: Well, I think -- I'd add Rick Perry in there, too.

(CROSSTALK)

BOLTON: I think their foreign policies are very, very similar. I wish we had had more debate, and perhaps there will be more among the Republican candidates because I think it's important to articulate these issues. But I think Governor Romney -- I've read his speeches and writings. I've talked to him about these issues over the years. I'm very confident about the strength of his view of American exceptionalism, the importance of a vigorous American role in the world to defend our interests, and I think he fully understands the challenges we face.

VAN SUSTEREN: In terms of -- and I realize that you have many disagreements with a Democratic president and President Obama. But what is the single most egregious, in your mind, foreign policy -- part of President Obama's foreign policy?

BOLTON: Well, I think on the big picture, he is comfortable with American decline in the world. He's comfortable with a receding, "Come home America." He's happy with a reduced defense budget. He doesn't appreciate that we face enormous risks and challenges, most immediately from the proliferation of weapons of mass destruction, but also from the threat long-term of a potentially aggressive China, a resurgent Russia, chaos in the Middle East. I just don't think he understands the world even after three years of on-the-job training.

VAN SUSTEREN: All right, let me separate out from your support and endorsement of Governor Romney -- I want to ask you about Iran. I asked Senator Santorum about it, the scientist who was killed in a bomb on the streets of Tehran. Ahmadinejad is blaming us. We've denied it. We've condemned it. Israel is silent. How -- how would you handle that?

BOLTON: Well, obviously, somebody's going after Iran's nuclear scientists, and what a shame that is, indeed. But the fact is that we are not taking adequate steps, not the United States, not the West as a whole, to stop Iran from achieving its objective of getting nuclear weapons.

Shortening the life expectancy of the occasional Iranian nuclear scientist is not going to stop their program. They are very close to getting it. The administration knows that. There's no chance sanctions are going to stop them...

VAN SUSTEREN: So why was this guy killed?

BOLTON: Well, I don't know who's -- I don't know who's responsible for it...

VAN SUSTEREN: Well, somebody who didn't like him. Somebody who didn't like the program, probably. I don't -- maybe it's an ex-wife, I don't know, but it sounds like -- it sounds more like it was related to his job.

BOLTON: I'm not losing any sleep over it, but I think what's even more interesting in response is Hillary Clinton saying the United States didn't have anything to do with this. Why did she say that? Because I think she fears Iranian retaliation.

Well, if you don't like the way Iran behaves now, threatening to kill the Saudi Arabian ambassador and those -- how do you think they're going to behave once they get nuclear weapons?

VAN SUSTEREN: Is there -- is her fear irrational, though, in light of the fact there was this plot to assassinate the Saudi ambassador here in the United States? I mean, so is her fear in any way, you know, out of line?

BOLTON: No, it's not irrational, but this is the regime that she and her president want to negotiate with, still operating after three years under the delusion they can chit-chat the Iranian regime out of its nuclear weapons program.

VAN SUSTEREN: Ambassador, thank you. And thank you for coming here to announce your support for Governor Romney. Thank you, sir.

BOLTON: Thank you.