Timeline: U.S.-Iran relations from 1953 coup to 2023 detainee swap deal

© Reuters. FILE PHOTO: USA and Iranian flags are seen in this illustration taken, September 8, 2022. REUTERS/Dado Ruvic/Illustration/file photo

DUBAI (Reuters) - The United States and Iran are to free five detainees each under an exchange agreement that also involves the transfer of $6 billion of unfrozen Iranian assets from South Korea to accounts in Qatar.

The deal removes one major irritant between Iran and the U.S., whose animosity dates back to the Central Intelligence Agency's orchestration of the overthrow of Iran’s popular Prime Minister Mohammed Mossadegh in 1953 and restoration of the Shah, Mohammed Reza Pahlavi, who became a staunch U.S. ally.

Following is a chronology of major events in relations between the Iran and the United States:

1953 - The CIA helps orchestrate overthrow of Iran’s popular Prime Minister Mohammed Mossadegh, restoring to power Shah Mohammed Reza Pahlavi.

1957 - The U.S. and Iran sign an agreement on civil nuclear cooperation.

1967 - The U.S. provides Iran with a nuclear reactor along with weapons-grade 93% enriched uranium fuel.

1968 - Iran signs the Nuclear Non-Proliferation Treaty which permits it 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 seize the U.S. Embassy in Tehran and hold staff hostage.

1980 - The U.S. cuts diplomatic ties with Iran, seizes Iranian assets and bans most trade with Tehran. Hostage rescue mission ordered by President Jimmy Carter fails.

1981 - Iran releases 52 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.

1988 - U.S. warship Vincennes mistakenly shoots down Iranian passenger plane over the Gulf, killing all 290 aboard.

2002 - President George W. Bush declares that Iran, Iraq and North Korea are an "axis of evil." U.S. officials accuse Tehran of operating secret nuclear weapons program.

2009 - Britain, France and the United States announce that Iran is building a secret uranium-enrichment site at Fordow.

2012 - U.S. law gives President Barack Obama the power to sanction foreign banks if they fail to significantly reduce imports of Iranian oil. Iranian oil sales drop, sparking an economic downturn.

U.S. and Iranian officials begin secret talks, which intensify in 2013, on the nuclear issue.

2013 - Hassan Rouhani is elected Iran’s president on a platform of improving Iran’s relations with the world and its economy.

2015 - Iran and six major powers reach a nuclear agreement, under which Tehran agrees to curb its nuclear work in return for sanctions relief.

2018 - President Donald Trump withdraws from the nuclear deal in May, and reimposes crippling economic sanctions on Iran.

2019 - In April, the U.S. designates the Islamic Revolutionary Guard Corps a "terrorist organization".

In May, Iran says it will increase enriched uranium production, bucking its commitments under the nuclear accord.

In September, Saudi Arabia’s state-run oil company is attacked by drones and missiles believed to be from Iran; Tehran denies involvement.

2020 - Iran vows harsh revenge after a U.S. air strike in Baghdad kills special forces commander Qassem Soleimani, architect of Iran's military influence in the Middle East.

2021 - U.S. and Iranian officials hold six rounds of indirect nuclear talks in Vienna between April and June. A new round begins on Nov. 29 after a five-month hiatus triggered by the election of Iran's hardline president Ebrahim Raisi.

2022 - Indirect talks between Tehran and Washington stall in September, leading both sides to sketch out steps that could free some detained U.S. citizens and unfreeze some Iranian assets abroad.

2023 - In August, Iran and the United States agree a swap of detainees and the unfreezing of $6 billion of Iranian assets in South Korea.