• With: Sen. John McCain, R-Ariz.

    This is a rush transcript from "Your World," September 16, 2014. This copy may not be in its final form and may be updated.

    (BEGIN VIDEO CLIP)

    CHUCK HAGEL, U.S. DEFENSE SECRETARY: I'm always concerned about our borders.

    SEN. JOHN MCCAIN, R-ARIZ.: I mean, is that a serious concern of yours?

    HAGEL: I think we have to always look at these things as serious concerns.

    (CROSSTALK)

    MCCAIN: In other words, do you think we have to improve our border security, especially on the southern border?

    HAGEL: We can improve our border security.

    (END VIDEO CLIP)

    NEIL CAVUTO, HOST: Did John McCain get the answer he wanted?

    The senator with us right now.

    Senator, what did you make of what the defense secretary was telling you?

    MCCAIN: Well, it was sort of symptomatic of the entire hearing, a lot of waffling around and nonanswers to the questions.

    The reason why I asked it, Neil, was because in a hearing a couple of days ago with the Department of Homeland Security, one of the witnesses who is directly in charge of border security said that there is a real concern about one of these or more of these terrorists who would come across our southern border.

    And the fact is, our southern border is not secure. They have already announced on Twitter and on Facebook that they want to do everything they can to attack the United States of America. So, if the southern border is not secure, obviously, that would be one of the avenues to achieve that, and which leads me to believe that we have to have 90 percent effective control of the border, and 100 percent situational awareness before we move forward with comprehensive immigration reform.

    This new ISIS threat has really heightened, in my view, the absolute requirement for a secure border, which we don't have.

    CAVUTO: When -- when Homeland Security made that ISIS remark about, yes, they could get through the border, what have you, we're watching it, do you think they were just sort of doing a little pre-heinie covering, that God forbid something happens, we have warned you that's a worry, we're out there saying it's a worry, we're watching it?

    What did you think of it? Because it came out of nowhere.

    MCCAIN: Well, the -- the -- since I raise -- posed the question with retired a Army general who works there for the secretary of homeland security, he is a very honest man. And I think he was giving me a pretty straightforward answer...

    (LAUGHTER)

    MCCAIN: ... as opposed the one I got from the secretary of defense.

    CAVUTO: You have been critical of late of Rand Paul, and I think in one line you said, you know, he hasn't even been to Syria.

    So when you hear him say that Hillary Clinton would have really botched it big-time had she gotten her way a year ago and we had gone ahead and funded the rebels who were trying to topple Assad, he more or less said -- I think I got the gist of what he said, Senator -- that you would be funding what would be a modern-day ISIS running Syria today.

    What did you think of that?

    MCCAIN: I think it's a fundamental lack of understanding of the situation and the threats we face.

    Senator Paul has obviously being doing some somersaults as these beheadings took place and the American people's opinion has shifted rather dramatically. He has even said that I met with ISIS, which is patently false.

    In fact, ISIS has called me the number one enemy when I went to Syria and met with these brave young men, some of whom are dead now. So, it's a -- I think it's kind of a desperation kind of trying to find some footing here as he slides down a very steep slope of credibility.

    CAVUTO: Do you think he is trying to just divorce himself from his more libertarian roots, certainly his father's roots, that has a no- interventionist type policy, that that isn't going jibe well in a presidential run, that this is all political?

    MCCAIN: I don't know. I think it's very clear that he has presidential ambitions, something that I shouldn't criticize.

    CAVUTO: Do you think he would be a good president? Do you think he would be a good commander in chief?

    MCCAIN: Not on -- not on national security, no, nor did I believe his father would either.

    His -- he has dramatically shifted his positions on national security. He said we shouldn't intervene, no matter what, anywhere. And now obviously he wants to take out ISIL. Well, if you want to take out ISIS, then you are going to have to take certain measures, and that means some very serious American involvement.

    CAVUTO: Now, he has said the distinction here is that if it's an immediate threat, by all means, engage. You say he is just trying to double-talk.

    MCCAIN: No.

    I just say I don't think he understands the nature of the threat. And I don't think he understands how serious it is and how, if we allow them to continue to metastasize and control a territory the size of the state of Indiana, with hundreds of millions of dollars, equipment, and now attracting thousands from all over the world, much less the Middle East, that they do, as our intelligence experts told us, pose a direct threat to the United States.

    We can't wait until there's another attack to say that -- obviously.

    CAVUTO: Do you trust Senator Paul?

    MCCAIN: I -- I don't -- it's not a matter of trust. It's matter of whether I agree or disagree with his view of the role of America in the world, just as I disagreed with his father's views.

    (CROSSTALK)