According to Foreign Policy, the American CIA staged the 1953 coup in which Prime Minister, Mohammad Mosaddeq, was overthrown. General Fazlollah Zahedi, who had collaborated with the Western intelligence services, became Prime Minster. Mohammad Reza Shah Pahlavi, who had fled into exile, was reinstated on the throne.
After six decades, US admitted that it had directly contributed to the coup. The document was initially published in 1981 in which CIA role had been blacked out.
According to the document which has been published on National Security Archive website, CIA started a wave of negative propaganda against Mosaddeq government in an attempt to depose him.
So far, two US presidents, Clinton and Obama, have admitted to CIA role. This is while some US officials believe that such statements would only cause strain in Washington-Tehran relations.
On August 15, 1953, the British and US intelligence agencies initiated a coup by the Iranian military (known as 28 Mordad coup), setting off a chain of events including riots in the streets of Iran’s capital, Tehran, that led to the overthrow and arrest of Mosaddeq four days later.
Mosaddeq, convicted of treason, served three years in prison and died under house arrest in 1967.