20 PHOTOS US Iran Nuclear Talks -- Congress -- John Kerry -- updated 5/22/2015 See Gallery GOP senators warning over US-Iran nuclear negotiations WASHINGTON, DC - APRIL 14: Senate Foreign Relations Committee Chairman Sen. Bob Corker (2nd L) (R-TN) gavels the start of a Senate Foreign Relations Committee markup meeting on the proposed nuclear agreement with Iran April 14, 2015 in Washington, DC. A bipartisan compromise reached by Corker and Sen. Ben Cardin (D-MD) would create a review period that is shorter than originally proposed for a final nuclear deal with Iran and creates compromise language on the removal of sanctions contingent on Iran ceasing support for terrorism. (Photo by Win McNamee/Getty Images) WASHINGTON, DC - APRIL 14: Senate Foreign Relations Committee Chairman Sen. Bob Corker (L) (R-TN) shakes hands with ranking member Sen. Ben Cardin (R) (D-MD) during a committee markup meeting on the proposed nuclear agreement with Iran April 14, 2015 in Washington, DC. A bipartisan compromise reached by Corker and Cardin would create a review period that is shorter than originally proposed for a final nuclear deal with Iran and creates compromise language on the removal of sanctions contingent on Iran ceasing support for terrorism. (Photo by Win McNamee/Getty Images) WASHINGTON, DC - APRIL 14: Sen. Rand Paul (R-KY) (Rear), a Republican presidential candidate, passes Sen. Marco Rubio (bottom), a Republican presidential candidate, as senators make their opening remarks during a markup meeting of the Senate Foreign Relations Committee on the proposed nuclear agreement with Iran April 14, 2015 in Washington, DC. A bipartisan compromise reached by Sen. Bob Corker (R-TN) and Sen. Ben Cardin (D-MD) would create a review period that is shorter than originally proposed for a final nuclear deal with Iran and creates compromise language on the removal of sanctions contingent on Iran ceasing support for terrorism. (Photo by Win McNamee/Getty Images) WASHINGTON, DC - APRIL 08: Acting U.S. State Department spokesperson Marie Harf conducts a daily press briefing at the State Department April 8, 2015 in Washington, DC. Harf spoke on various topics including the Iran nuclear deal. (Photo by Alex Wong/Getty Images) US President Barack Obama makes a statement at the White House in Washington, DC, on April 2, 2015 after a deal was reached on Iran's nuclear program. Iran and world powers agreed on the framework of a potentially historic deal aimed at curbing Tehran's nuclear drive after marathon talks in Switzerland. (Photo credit: NICHOLAS KAMM/AFP/Getty Images) WASHINGTON, DC - APRIL 02: A teleprompter shows the text for U.S. President Barack Obama's remarks on negotiations with Iran over their nuclear program on April 2, 2015 in Washington, DC. In exchange for Iran's agreement to curb their country's nuclear proliferation, the United States would lift some of the crippling sanctions imposed. (Photo by Win McNamee/Getty Images) WASHINGTON, DC - APRIL 2: U.S. President Barack Obama boards Air Force One after making a statement on Iran nuclear negotiations in the White House April 2, 2015 in Washington, DC. The so-called P5+1 nations reached an agreement for an Iranian nuclear program and a process to lift sanctions against Iran after talks in Switzerland. (Photo by Olivier Douliery-Pool/Getty Images) US Secretary of State John Kerry (C) walks with bodyguard in the garden of the Beau-Rivage Palace hotel during a break in Iran nuclear talks in Lausanne, Switzerland, on April 1, 2015. Rollercoaster talks aimed at stopping Iran getting a nuclear bomb went into extra time amid cautious signs that after seven days of tough negotiations a framework deal may be near. (Photo credit: ABRICE COFFRINI/AFP/Getty Images) US Secretary of State John Kerry (L) gestures while waiting for the opening of a plenary session with P5+1 ministers, European Union and Iranian minister on Iran nuclear talks at the Beau Rivage Palace Hotel in Lausanne, Switzerland, on March 31, 2015. Foreign ministers from major powers kicked off early a final scheduled day of talks aimed at securing the outlines of a potentially historic nuclear deal with Iran by a midnight deadline. (Photo credit: FABRICE COFFRINI/AFP/Getty Images) LAUSANNE, SWITZERLAND - MARCH 31: P5+1 Ministers, European Union and Iranian officials wait for the opening of a plenary session on Iran nuclear talks at the Beau Rivage Palace Hotel on March 31, 2015. (Photo by Thomas Trutschel/Photothek via Getty Images) LAUSANNE, SWITZERLAND - MARCH 31: German Foreign Minister Frank-Walter Steinmeier waits for the opening of a plenary session on Iran nuclear talks P5+1 Ministers, European Union and Iranian officials at the Beau Rivage Palace Hotel on March 31, 2015. (Photo by Thomas Trutschel/Photothek via Getty Images) WASHINGTON, USA - FEBRUARY 5: Senator Tom Cotton speaks during a news conference with members of the Senate Armed Services Committee about arming Ukraine in the fight against Russia in Washington, D.C. on February 5, 2015. (Photo by Samuel Corum/Anadolu Agency/Getty Images) WASHINGTON, DC - MARCH 03: Israeli Prime Minister Benjamin Netanyahu (3rd L) poses for photographers with U.S. Senate Majority Leader Sen. Mitch McConnell (R-KY) (2nd L), Senate Minority Leader Sen. Harry Reid (D-NV) (4th L), Senate Majority Whip Sen. John Cornyn (R-TX) (L) and Minority Whip Sen. Richard Durbin (DIL) (R) prior to a meeting at the U.S. Capitol March 3, 2015 in Washington, DC. At the risk of further straining the relationship between Israel and the Obama Administration, Netanyahu addressed a joint meeting of the U.S. Congress warning congressional members against what he considers an ill-advised nuclear deal with Iran. (Photo by Alex Wong/Getty Images) WASHINGTON, DC - MARCH 3: Israel's Prime Minister Benjamin Netanyahu speaks before joint session of Congress, on March, 03, 2015 in Washington, DC. (Photo by Bill O'Leary/The Washington Post via Getty Images) US Secretary of State John Kerry (Far R) goes for a stroll with assistant and security on the shore of Lake Geneva upon his arrival on February 22, 2015 in Geneva. Kerry arrived in Geneva for renewed talks with his Iranian counterpart on Tehran's nuclear programme, after warning 'significant gaps' remain as a key deadline approaches. Kerry is set to sit down for two days of talks with Iranian Foreign Minister Mohammad Javad Zarif, whose country denies its nuclear programme has military objectives. (Photo credit: FABRICE COFFRINI/AFP/Getty Images) US Secretary of State John Kerry (L) arrives at his hotel on February 22, 2015 in Geneva. Kerry arrived in Geneva for renewed talks with his Iranian counterpart on Tehran's nuclear programme, after warning 'significant gaps' remain as a key deadline approaches. Kerry is set to sit down for two days of talks with Iranian Foreign Minister Mohammad Javad Zarif, whose country denies its nuclear programme has military objectives. (Photo credit: FABRICE COFFRINI/AFP/Getty Images) US Secretary of State John Kerry (R) walks back to his hotel after on February 23, 2015 in Geneva. Washington and Tehran's top diplomats sat down again on February 23 for talks on Iran's nuclear program as they struggled to narrow gaps ahead of a key deadline. (Photo credit: FABRICE COFFRINI/AFP/Getty Images) US Secretary of State John Kerry (C) goes for a stroll with assistants and security along the shores of Lake Geneva upon his arrival on February 22, 2015 in Geneva. Kerry arrived in Geneva for renewed talks with his Iranian counterpart on Tehran's nuclear programme, after warning 'significant gaps' remain as a key deadline approaches. Kerry is set to sit down for two days of talks with Iranian Foreign Minister Mohammad Javad Zarif, whose country denies its nuclear programme has military objectives. (Photo credit: FABRICE COFFRINI/AFP/Getty Images) LONDON, UNITED KINGDOM - FEBRUARY 21: U.S. Secretary of State John Kerry speaks during a media briefing at the U.S. Embassy on February 21, 2015 in London, England. Earlier Kerry met with British Foreign Minister Philip Hammond and it's expected that the issue of the continuing conflict in the Ukraine will dominate talks between the two nations. (Photo by Neil Hall - Pool/Getty Images) Is the U.S. being too soft on Iran when negotiating on sanctions and a potential nuclear deal? Strategic Policy Consulting's Alireza Jafarzadeh and WSJ's Simon Constable discuss. Up Next See Gallery Discover More Like This HIDE CAPTION SHOW CAPTION of SEE ALL BACK TO SLIDE

WASHINGTON (AP) -- Forty-seven Republican senators warned Monday that any agreement the Obama administration strikes with Iran to limit Tehran's nuclear program may be short-lived unless Congress approves the deal.

In an open letter to Iranian leaders, Sen. Tom Cotton, R-Ark., and 46 other Republicans said that without congressional approval, any deal between Iran and the U.S. would be merely an agreement between President Barack Obama and Iran's supreme leader, Ayatollah Ali Khamenei.

"The next president could revoke such an executive agreement with the stroke of a pen," they wrote, "and future Congresses could modify the terms of the agreement at any time."

Though the letter is addressed to leaders in Tehran, it seems as much aimed at delivering a message to Obama.

Republicans and some Democrats want Congress to vote on any agreement. The pact the bargainers are working on does not require congressional approval because it is not a treaty, which would require a two-thirds majority Senate vote to be ratified.

The U.S. and other nations are seeking a pact that would let Western powers verify that Iran will not obtain a nuclear weapon.

The next negotiations are scheduled for March 15, and wide gaps remain between the two sides. The deadline for an outline of a U.S.-Iranian deal is at the end of March.

Iran has said its nuclear program is peaceful and is aimed at producing energy.

There was no immediate Iranian government reaction to the letter or any discussion of it in Iranian media.

Cotton is a freshman senator who serves on the Senate's Armed Service and Intelligence committees.



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