After arduous talks that spanned 20 months, negotiators reached a landmark deal aimed at reining in Iran's nuclear program, announced on July 14. From left, European Union High Representative for Foreign Affairs and Security Policy Federica Mogherini, Iranian Foreign Minister Mohammad Javad Zarif, Head of the Iranian Atomic Energy Organization Ali Akbar Salehi, Russian Foreign Minister Sergey Lavrov, British Foreign Secretary Philip Hammond and U.S. Secretary of State John Kerry pose for a group picture at the United Nations building in Vienna on July 14.
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U.S. Secretary of State John Kerry has been spearheading negotiations on a possible deal to rein in Iran's nuclear program.
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Kerry, second from left, meets Iranian Foreign Minister Mohammad Javad Zarif, second from right, for talks in Lausanne, Switzerland, on Monday, March 16. At the far left is U.S. Secretary of Energy Ernest Moniz. At the far right is Ali Akbar Salehi, head of Iran's Atomic Energy Organization.
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Iranian Supreme Leader Ayatollah Ali Khamenei meets with environmental officials in Tehran, Iran, on Sunday, March 8.
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Iranian President Hassan Rouhani speaks in September during a news conference in New York.
Wendy Sherman has been a key U.S. negotiator in the Iran talks. She is the under secretary of state for political affairs.
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Federica Mogherini, foreign policy chief for the European Union, has been representing the Europeans in nuclear talks with Iran.
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Iran's parliament speaker Ali Larijani listens to a question during a news conference in Tehran on March 16.
Yukiya Amano is director general of the International Atomic Energy Agency, the U.N.'s nuclear watchdog.
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Iran and world powers comprising the P5+1 negotiating team meet in Montreux, Switzerland, on Thursday, March 5.