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This is a RUSH transcript from "The O'Reilly Factor," September 19, 2014. This copy may not be in its final form and may be updated.

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O'REILLY: And in the "Impact" segment tonight there's no question that fighting terrorism overseas is a complicated dangerous situation which President Obama and many Americans would rather avoid. Enter, Senator Rand Paul who believes because the U.S. got involved in Iraq and Afghanistan and other places, terrorism has been given a big push.

Recently Mr. Paul told the "Daily Beast" Web site that John McCain has actually met with ISIS representatives in Syria. The "The Washington Post" investigated that claim and found it to be false.

Joining us now from Phoenix, Arizona is Senator McCain. So, let's get the deal with Rand Paul out of the way first. You guys fundamentally disagree about how to fight terrorism. But now it's getting a little personal. What's the deal?

SEN. JOHN MCCAIN (R), ARIZONA: I don't -- frankly, I don't understand why Senator Paul would echo things from the Internet. You just had previous commentaries on it that is absolutely false and conveyed on the Internet by enemies of the United States. I would remind that you ISIS on their Internet said that -- on the Internet said that I was their worst enemy. The crusader, John McCain.

So what, unfortunately Senator Paul has made statements about my actions which are totally false. "The Washington Post" gave him four Pinocchios and said they wish they could give more because it was absolutely false. So I don't know why Senator Paul would do that. All he had to do was come and ask me if it was true.

I respect Senator Paul's views on what America should be doing in this fight against this horrible terrorism which has now metastasized in Syria and Iraq. But I don't understand why he should say things that are patently false about me and that's, that's frankly, a bit disturbing because that's not how I'm used to working in the United States Senate.

O'REILLY: All right and he's is in your party as well. All right, now, you did meet with Syrian moderates who were fighting against ISIS and Assad. That's who you met with, right?

MCCAIN: Yes the members of the Free Syrian Army and I might point out because of the President's decision not to provide them with arms, a number of those brave young men are dead now that I met with -- yes.

O'REILLY: Ok. I am skeptical that the Free Syrian Army can defeat ISIS at this juncture maybe if we had armed and trained them three or four years ago, possible but not now. I don't think that can be done. Am I wrong?

MCCAIN: I believe you're wrong but it's much more difficult. You are right in that respect so many of them have been killed because we refused to help them. Now we're telling them he we'll train them and equip them and send them about 5,000 thousand and by the way, there are 31,000 ISIS.

O'REILLY: Yes but I don't know how the numbers don't match.

MCCAIN: But we're sending them into an environment where Bashar Assad can kill them from the air. That's not -- that's not fair to them. That's just wrong.

O'REILLY: Well we should have taken -- long time ago off the gas can.

MCCAIN: We should exactly, exactly.

O'REILLY: You and I -- you and I agree on foreign policy with a couple of exceptions. But the problem that you and Senator Lindsey Graham who we're going to have us on a bit later on, the problem that you guys have is that you were very bullish on the Iraq invasion and the Afghan campaign and a lot of Americans say look, it just didn't work to our advantage.

So, now, when you talk you have that almost on your back.

MCCAIN: Well, first of all, let me point out that -- that everyone knows we should have gone to Afghanistan where the attacks of 9/11 started.

O'REILLY: I know but it isn't working out.

MCCAIN: It's almost overwhelming -- well, actually, if we would leave a residual force behind, it is going to work out. If we don't, it's going to be Iraq over again.

In the case of Iraq, we're the ones that said Rumsfeld should resign that we had to do the surge. The surge succeeded. The situation was stable. And if we had left a force behind, the kind that the President should be reconstituting now, we wouldn't be where we are today, Bill.

O'REILLY: I know but even if had done that.

MCCAIN: We had it won. Yes we had it won. I guarantee you I was there. There is no doubt about that.

O'REILLY: And I -- I agree with you. But the price that was paid has soured Americans from supporting more action in that chaotic part of the world and that's a fact all the polls show it.

So now it's hard to get their attention to do what's necessary to defeat ISIS. You see what I'm saying.

MCCAIN: Of course. I know exactly what you mean. And I hear it from my constituents all the time. I think these beheadings have obviously -- and the polls show it. You have echoed, referred to those polls on your show, that there has been a drastic change in American attitude because they are deeply concerned about them being able to attack the United States of America as Mr. Baghdadi said after he left our prison, Camp Bucca and he said see you in New York. I believe them.

O'REILLY: Yes.

MCCAIN: And look what's happening in Australia right as we speak.

O'REILLY: I know. I know Australia there is a plot or was a plot that was uncovered by the authorities to behead people there to send a message.

Now I'm going to give you a chance to talk about Ukraine in a second just for a brief time.

MCCAIN: Sure.

O'REILLY: But I want to say one more thing on the ISIS thing. The way to beat these guys and I think you agree with me is to put together a good mercenary army, all right, paid for by Saudi Arabia and other rich Gulf states. All right, a real first class mercenary army with American advisors and hunt these guys can down. That's how you do it and then with help from the air. Am I wrong?

MCCAIN: You are right. But you've got to take Bashar Assad's air assets otherwise you --

(CROSSTALK)

O'REILLY: Right you've got to bomb -- that can be done in 24 hours. And it should have been done on the gas situation. All right, Ukraine. You have 35 seconds. Why should we care?

MCCAIN: Ok.

The President of Ukraine gave one of the most moving powerful speeches I have ever seen to Congress yesterday begging for our help. His country has been dismembered, and guess what -- we will still not provide them with lethal weapons. That is so shameful I can't tell you, Bill.

O'REILLY: All right Senator, we appreciate your time.

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