This is a rush transcript from "On the Record," March 11, 2015. This copy may not be in its final form and may be updated.
GRETA SUSTEREN, FOX NEWS HOST: Today, Secretary of State John Kerry hammering the 47 GOP senators for writing that letter to Iran's leaders in the middle of ongoing nuclear talks.
JOHN KERRY, SECRETARY OF STATE: My reaction to the letter was utter disbelief.
JOSH EARNEST, WHITE HOUSE PRESS SECRETARY: Attempting to sandbag the president of the United States in the midst of negotiations is not just unprecedented but inappropriate.
SEN. TOM COTTON, R-AR: The only thing unprecedented is an American president negotiating a nuclear weapons deal with the world's leading state sponsor of terrorism without seeking congressional approval.
KERRY: To write to the leaders in the middle of a negotiation.
EARNEST: Senator McCain just last night said it was maybe not the most effective thing that they could do.
SEN. JOHN MCCAIN, R-ARIZ: I think that Iranians should know that that the Congress of the United States has to play a role.
KERRY: They're going to give a constitutional lesson which, by the way, was absolutely incorrect. It's quite stunning.
SUSTEREN: That letter was Senator Tom Cotton's idea signed by 47 Republican senators. The letter has been criticized by President Obama. Secretary of State John Kerry and Secretary of State Hillary Clinton, and she took it one step further today, to Twitter.
Secretary Clinton tweeting "GOP letter to Iranian clerks undermines American leadership. No one considering rung for commander and chief should be signing on."
And Senator Cotton firing back, "No, Hillary Clinton, letter to Iran helps protect U.S.A. from bad deal. No commander and chief should allow world's worst regimes to get world's worst weapon."
Senator Cotton joins us. Nice to see you, sir.
SEN. TOM COTTON, R-AR: Good to see you, Greta.
SUSTEREN: That was an interesting Twitter spat.
COTTON: Well, the simple fact of the matter is the deal the president has proposed and we know two terms of it are unacceptable for the U.S. and the world. He would accept a 10-year sunset on a deal and he would allow Iran to have a vast uranium enrichment capability which is a critical component of a nuclear weapon. The U.S. is focused on stopping Iran from getting a nuclear bomb not just today and tomorrow but 10 and 15 years from now.
SUSTEREN: I want to go back to the Twitter from her Secretary of State Hillary Clinton. She says, "Anyone who is thinking of running G.O.P. candidate in 2016 shouldn't be signing on to this." What do you say to that?
COTTON: I'm surprised that Secretary Clinton who herself senator is not standing up for Constitutional powers of the Congress. I'm sure when she was in the Senate she felt differently. The founders created our Constitution with separation of powers to make sure that no president, whoever he or she may be can bind the United States to an international agreement without congressional approval.
Now, I think it's important for the American people to know that Secretary Clinton supports Barack Obama's approach to these negotiations and supports the terms of the deal that would allow Iran to get a nuclear weapon.
SUSTEREN: Is the deal with Iran, assuming that there is one. We haven't seen it is that a treaty?
COTTON: Whether it's a treaty or congressional executive agreement.
SUSTEREN: What is a treaty?
COTTON: There is both the treaty and congressional executive agreement. Treaty requires two thirds votes of the Senator. A congressional executive agreement can be a majority vote of both houses so that can be debated. That's not the point we are discussing.
Barack Obama proposes to do something called executive agreement, which is the third kind of international agreement. And executive agreement is not binding on a future Congress or president or the country makes a difference to me.
SUSTEREN: I'm curious you are Harvard Law professor. What would you say? If you were teaching a Harvard Law class --
COTTON: It's a major nuclear agreement not with a friendly nation but state sponsor of terrorism. I would like to see a 667 bill threshold. Certainly there needs to be a majority vote, at least a majority vote. President Obama is proposing to have no vote at all.
President Obama himself has rescinded previous executive agreements such as the agreement that George Bush and Ariel Sharon reached in 2004 because it didn't have -- because it didn't have binding congressional approval.
SUSTEREN: Why do you have to do it this way and become pen pals essential with the Iran leadership? You could have put it in the "New York Times" or "The Washington Post" letter and they would have read it.
But you know here it does look like you are end-running the president. The president is end-running the Senate by saying is he not going to get your approval. Why are you doing that?
COTTON: We made an open letter as Lindsey Graham said not only the Iranian leadership but the entire world knows where we stand, and if you talk to most --
SUSTEREN: Who does it address?
COTTON: It's an open letter to the leaders of the Islamic Republic of Iran.
SUSTEREN: So it's to them.
SUSTEREN: If you put the same thing in the "New York Times" and had 47 senators say the president doesn't have the authority to do this or just a piece of paper, as soon as he leaves we can tear it up and move on. If you done that you would have the same effect, you wouldn't have bypassing the president and having that symbolic gesture of going directly to Iran.
COTTON: Well, two things, first, if you talk to most Iran experts they will tell that you Iran senior leadership doesn't understand our constitutional system of government.
SUSTEREN: They could have read it in the "New York Times" or "The Washington Post."
COTTON: We wanted to make crystal clear they heard that.
SUSTEREN: I'm not kidding. I was in North Korea. The North Koreans were reading things about Fox News in the "New York Times" that they confronted me about. They are all watching us.
COTTON: We wanted to make sure it was crystal clear they heard it because I also worry that they're not hearing that at the negotiations in Geneva or -- their foreign minister is not communicating it back to the senior leader in Iran.
If you look at the response to our letter it goes to show that we need to send the letter in the first place. Goes to show he doesn't understand America's constitutional separation of powers while president negotiates it's the Congress that approves agreements.
SUSTEREN: So you have no regrets about the methodology about going directly to the Iranian leadership.
COTTON: No regrets at all. We're trying to stop Iran from getting a nuclear weapon and Iran has to understand that the Congress will protect the American people from a bad deal as they have been doing for 200 years and as our founding fathers envisioned.
SUSTEREN: Senator, nice to see you sir, thank you.
COTTON: Nice to see you, Greta.