REUTERS - The United States lifted nuclear-related sanctions on Iran on Saturday after the International Atomic Energy Agency certified Tehran had taken steps to limits its nuclear activities under a July 2015 agreement.
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In a related diplomatic deal between the two long-time adversaries, Iran freed five detained Americans and U.S. President Barack Obama granted clemency to at least seven Iranians convicted in U.S. courts or awaiting trial.
Following is a chronology of major events in relations between the Iran and the United States:
1953 - CIA helps orchestrate overthrow of Iran's popular Prime Minister Mohammed Mossadegh, restoring to power the Shah, Mohammed Reza Pahlavi.
1957 - The United States and Iran sign an agreement on civil nuclear cooperation.
1967 - The United States provides Iran with the Tehran Research Reactor (TRR), a 5-megawatt nuclear reactor along with weapons-grade 93 percent enriched uranium fuel.
1968 - Iran signs the Nuclear Non-Proliferation Treaty (NPT) which, when ratified two years later, permits Iran to have a civil nuclear program in return for a commitment not to acquire nuclear weapons.
1979 - Iran's Islamic Revolution forces U.S.-backed Shah to flee, Ayatollah Ruhollah Khomeini returns from exile and becomes supreme religious guide. Fundamentalist students demanding Washington hand over the Shah for trial seize the U.S. embassy in Tehran on Nov. 4 and hold staff hostage for 444 days.
1980 - United States cuts diplomatic ties with Iran, seizes Iranian assets and bans most trade with it. U.S. hostage rescue mission ordered by President Jimmy Carter fails when helicopter crashes in sandstorm and eight U.S. servicemen are killed.
1981 - Iran releases U.S. hostages minutes after Carter steps down and Ronald Reagan is inaugurated as U.S. president.
1984 - U.S. lists Iran as a state sponsor of terrorism.
1986 - Reagan reveals secret arms deal with Tehran in violation of U.S. arms embargo. Money from the sales was secretly passed to anti-communist guerrillas in Nicaragua.
1988 - U.S. warship Vincennes mistakenly shoots down Iranian passenger plane over the Gulf, killing all 290 aboard.
2000 - Secretary of State Madeleine Albright acknowledges the damage done by the U.S. role in the Mossadegh coup, saying: "It is easy to see now why many Iranians continue to resent this intervention by America in their internal affairs."
2002 - President George W. Bush declares Iran, Iraq, North Korea an "axis of evil." U.S. officials accuse Tehran of operating secret nuclear weapons program.
-- An Iranian exile group opposed to the government in Tehran reveals that Iran had two previously undisclosed nuclear facilities under construction: a uranium-enrichment plant at Natanz and a heavy water-moderated nuclear reactor at Arak.
2006 - Washington says willing to join multilateral nuclear talks with Iran if it verifiably suspends nuclear enrichment.
2007 - May - Iranian Foreign Minister Manouchehr Mottaki and U.S. Secretary of State Condoleezza Rice chat briefly on the sidelines of conference in Egypt.
December - A U.S. National Intelligence Estimate assesses with high confidence that Iran was working to develop nuclear weapons until the fall of 2003, when it halted weapons work.
2008 - U.S. President George W. Bush for the first time sends an official, Under Secretary of State Bill Burns, to directly take part in nuclear negotiations with Iran in Geneva.
2009 - U.S. President Barack Obama takes office and tells Iran's leaders he would extend a hand if they would "unclench their fist" and persuade the West they were not trying to build a nuclear bomb.
Britain, France and the United States announce that Iran is building a secret uranium-enrichment site at Fordow, near the Shi'ite Muslim holy city of Qom. Iran says it disclosed the site to the UN nuclear watchdog earlier in the week.
2009-2012 - Nuclear negotiations between major powers and Iran largely stall.
2012 - U.S. law goes into effect giving Obama the power to sanction foreign banks, including the central banks of U.S. allies, if they fail to significantly reduce their imports of Iranian oil. The result is a drastic reduction in Iranian oil sales and a sharp downturn in the Iranian economy.
U.S. and Iranian officials begin secret talks, which intensify in 2013, on the nuclear issue.
2013 - Pragmatist Hassan Rohani is elected Iran's president on platform of improving Iran's relations with the world and its economy, something that can only be achieved by easing sanctions imposed because of Iran's nuclear program.
On Sept. 28, Obama and Rohani speak by telephone in the highest-level contact between the two countries in three decades.
On Nov. 23, with the groundwork laid by the secret U.S.-Iran talks, Iran and six major powers reach an interim pact called the Joint Plan of Action (JPOA) under which Iran agreed to curb its nuclear work in return for limited sanctions relief.
The six powers are the United States, Britain, China, France, Germany and Russia.
2015 - On July 14, Iran and the six powers strike an agreement, under which Iran agreed to take a series of steps, including slashing its number of centrifuges and disabling a key part of its Arak nuclear reactor - in return for significant easing of U.S., UN and EU sanctions.
The deal is called the Joint Comprehensive Plan of Action (JCPOA).
2016 - On Jan. 14, Iran releases 10 U.S. sailors, who ended up in Iranian territorial waters on two small boats, less than 24 hours after Iran took them into custody.
On Jan. 16, the United States and Iran announce a prisoner swap. Four Americans imprisoned in Iran are freed in return for clemency for at least seven Iranians, most of whom are dual U.S.-Iranian nationals, who were convicted or awaiting trial in the United States. A fifth American is released separately.
Later, the International Atomic Energy Agency confirms Iran had taken steps to restrict its nuclear activities required under the JCPOA. The United States lifts nuclear-related sanctions on Iran