MELISSA BLOCK, HOST:
On Capitol Hill today, another sign that Congress remains fixated on Iran. Earlier this week, 47 Republican senators wrote a letter to Iran's leaders warning that a nuclear deal between the U.S. and Iran could be undone by the next American president. Then this morning, there was a Senate hearing that was supposed to focus on the legal basis for the U.S. war against the self-proclaimed Islamic State. But as NPR's David Welna reports, that was practically an afterthought. Republicans mostly wanted to talk about Iran.
DAVID WELNA, BYLINE: It got started with Foreign Relations Committee Chairman Bob Corker. The Tennessee Republican recently traveled to Iraq. And he said one thing there really jumped out at him - how the U.S. is allowing Iran's influence in Iraq to keep growing.
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SENATOR BOB CORKER: Every single thing that we're doing is really enuring to the benefit of Iran. In other words, we're making Iraq a better place for Iran.
WELNA: Joint Chiefs of Staff Chairman General Martin Dempsey readily acknowledged Iran's growing military clout in the campaign against the Islamic State, which he referred to as ISIL. But that in itself, he said, is not a bad thing.
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GENERAL MARTIN DEMPSEY: I think there's general consensus, both inside of our own forces and also with the coalition partners with whom I engage, that anything anyone does to counter ISIL is in the main a good outcome. In other words, the activities of the Iranians - the support for the Iraqi security forces is a positive thing in military terms against ISIL.
WELNA: But also, according to Wisconsin Republican Ron Johnson, for Iran to become the dominant power in the region may not be a good thing.
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SENATOR RON JOHNSON: If it's Iran that is at the tip of the spear here - if they're the one sponsoring the victories, they're going to have influence in Iraq. And that's going to be very difficult, very dangerous for the regional peace, correct?
WELNA: Secretary of State John Kerry used Johnson's concerns to make a broader point.
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JOHN KERRY: If you're concerned about it now, think of what happens -and I hear this - we heard in the floor of the House recently, and you hear it elsewhere - if they had a nuclear weapon and they were doing that. That's why this administration believes the first step is to prevent the access to the nuclear weapon or prevent their ability to develop a nuclear weapon.
WELNA: At this point, the two issues got linked - the fight against ISIS and the nuclear negotiations with Iran. Florida Republican Marco Rubio said the desire for a deal has the administration pulling its punches.
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SENATOR MARCO RUBIO: I believe that much of our strategy with regards to ISIS is being driven by a desire not to upset Iran so that they don't walk away from the negotiating table and the deal that you're working on. Tell me why I'm wrong.
KERRY: Because the facts completely contradict that. But I'm not at liberty to discuss all of them here.
WELNA: Rubio refused to back down.
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RUBIO: The way we proceeded with our negotiations in Iran have impacted our trust level with these critical allies in this coalition.
KERRY: Senator, that actually is flat wrong - also, flat wrong.
RUBIO: They said so publicly.
KERRY: Just - it's flat wrong. I just came back from a meeting in the Gulf and Riyadh. I met with all of the GCC members. They all sat around the table. And they all articulated their support for what we're doing. And they believe we are better off trying to prevent them from getting a bomb diplomatically first, providing, of course, that it actually prevents them from getting that bomb.
WELNA: Kerry said the open letter that 47 Republican senators sent to Iran's leaders did not help.
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KERRY: My reaction to the letter was utter disbelief. During my 29 years here in the Senate, I never heard of nor even heard of it being proposed - anything comparable to this.
WELNA: Republicans on the panel shrugged off Kerry's outrage. Kentucky's Rand Paul said the letter was really meant for someone down Pennsylvania Avenue.
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SENATOR RAND PAUL: The letter was to Iran, but it should've been CCed to the White House, because the White House needs to understand that any agreement that removes or changes legislation will be have to be passed by us.
WELNA: Today's hearing was ostensibly about another piece of legislation - a new authorization to use force against the Islamic State. Its prospects may be dimming amidst the rancor over Iran. David Welna, NPR News, Washington. Transcript provided by NPR, Copyright NPR.