1967: Iran’s first nuclear reactor begins operation.
1970: Iran’s parliament ratifies nuclear nonproliferation treaty.
1979: The Iranian revolution results in a severing of U.S.-Iranian ties.
1984: U.S. adds Iran to its list of state sponsors of terrorism.
1992: Congress prohibits transfer of technology that might aid Iran’s weapons proliferation.
1996: Congress penalizes U.S. investments topping $20 million per year in Iran’s energy sector.
2003: International Atomic Energy Agency calls for Iran to suspend all uranium enrichment. Iran agrees to do so.
2004: IAEA rebukes Iran for failing to cooperate with nuclear inspectors.
2005: Russia agrees to provide fuel for an Iranian reactor; Iran promises to return spent nuclear fuel to Russia. IAEA finds Iran in noncompliance.
2006: IAEA asks United Nations Security Council to force Iran to suspend enrichment activities and cooperate with investigators. Iran announces that it has enriched uranium for the first time.
2007: IAEA, Iran agree on plan for Iran to share details about its nuclear activities. U.S. says Iran ended nuclear weapons program in 2003.
2009: Iran announces first satellite launch, raising concerns about its ballistic missile potential. U.S. agrees to participate in talks with Iran. Western officials accuse Iran of building a secret, second uranium-enrichment facility.
2010: U.N., Congress expand sanctions against Iran.
2011: U.S. intelligence officials tell Congress that Iran has not decided whether to pursue nuclear-weapons development.
2012: Talks with Iran begin. Israeli Prime Minister Benjamin Netanyahu draws a “red line” for an attack on Iran if it develops a nuclear bomb.
2013: Talks continue and details of an agreement emerge.
2014: Negotiations on comprehensive agreement extended until 2015.