The coup that overthrew Mossadegh and his National Front cabinet "was carried out under CIA direction as an act of U.S. foreign policy, conceived and approved at the highest levels of government," the document said. It was obtained by George Washington University's National Security Archive through the Freedom of Information Act.
"The coup was the beginning of a sequence of tragedies that dog the U.S. and its allies in the Middle East today," former CIA operative Robert B. Baer said.
"It was the key source of the anti-American resentment that exploded during the Iranian revolution of 1979," Baer, author of "The Devil We Know: Dealing With the New Iranian Superpower," told Al Jazeera.
"The military coup that overthrew Mosadeq and his National Front cabinet was carried out under CIA direction as an act of U.S. foreign policy, conceived, and approved at the highest levels of government," the document, obtained by George Washington University's National Security Archive through a Freedom of Information Act -- said using an alternative spelling of Mossadegh.
"The coup was the beginning of a sequence of tragedies that dog the U.S. and its allies in the Middle East today. It was the key source of the anti-American resentment that exploded during the Iranian revolution of 1979," Former CIA operative Robert B. Baer, author of "The Devil We Know: Dealing With the New Iranian Superpower," told Al Jazeera.
Pahlavi, a close U.S. ally, was toppled in the 1979 revolution. Its leadership under Ayatollah Ruhollah Khomeini made hostility toward the U.S. a cornerstone of Iran's foreign policy. The most immediate traumatic expression of that hostility was the hostage crisis that saw a group of Iranian students take control of the U.S. embassy in Tehran and hold 52 Americans captive for 444 days.
"Iranians truly believe that if it weren't for the CIA, the Shah would never have been brought to power," Baer said. "And they believe that the CIA continues to operate as an evil force in their country."
The CIA's role in the coup has long been known: A heavily redacted version of the document was first released in 1981 and there are still documents related to the coup that have not been released. But those released on Sunday -- the coup's 60th anniversary -- were the most explicit admission to date of involvement by the agency.
Reza Marashi, a former Iran analyst with State Department who is now with the National Iranian American Council, told Al Jazeera that the release of the documents could serve as a "very small, but important step forward in un-poisoning things."
"The first step toward fixing a problem is acknowledging it exists, and the problem that exists between Iran and the United States is historical – not just about centrifuges and everything else," Marashi said, referring to the ongoing fracas over Iran’s nuclear program. "You have to acknowledge the past in order to focus on the future – both sides need to do that."
Mossadegh had angered Britain by moving to take over the Anglo-Iranian Oil Company -- the predecessor of modern-day BP. The British believed that control of Iranian oil was vital to reviving their economy from the destruction of World War II.
The internal CIA history offered a degree of understanding of Mossadegh's position and rejected Western media depictions of him as "a madman" or "an emotional bundle of senility."
Another internal history, authored by coup planner Donald Wilber and leaked to The New York Times in 2000, said that agents had arranged stories against Mossadegh in the press both in Iran and the United States aimed at setting the stage for the coup.
In 2000, as part of an effort to mend relations with Iran, then-Secretary of State Madeleine Albright admitted that the U.S. had "played a significant role" in overthrowing Mossadegh. "The coup was clearly a setback for Iran's political development, and it is easy to see now why many Iranians continue to resent this intervention by America in their internal affairs," Albright said at the time.
President Barack Obama also made a similar admission after taking office in 2009 in another unsuccessful attempt at reconciliation with Iran, which has sought an explicit apology.
Historians often regard the 1953 coup in Iran as a first for the CIA, offering a template for government takeovers in Latin America and elsewhere during the Cold War.
Malcolm Byrne, deputy director of the National Security Archive, said that the CIA wrote the secret histories for internal use.
The histories "give people on the inside a sense of what happened and, presumably, give them a little context for whatever else they may be planning," he said.
U.S. and British spies also tried to fan the flames against Mossadegh among the Iranian clergy, the documents said. The history also said that the CIA arranged to pay $5 million within days of the coup to the new government of Fazlollah Zahedi, a general appointed to succeed Mossadegh.
While recognizing that London needed the oil, the CIA history said that British policymakers had "little in their experience to make them respect Iranians, whom company managers and Foreign Office managers saw as inefficient, corrupt and self-serving."
But the CIA history cast the decision in Cold War terms, fearing that the Soviets would invade and take over Iran if the crisis escalated and Britain sent in warships -- as it would do three years later alongside France and Israel when Egypt nationalized the Suez Canal.
"The irony was that the coup was predominantly a British operation, undertaken on behalf of that country's oil interests, into which the CIA was drawn in the name of anti-communism and fear that Mossadegh would hand the country over to the Russians," Baer said.
As for the timing of the document release, Marashi said it may have been a small and subtle gesture to Iran's new president Hassan Rouhani, who has vowed to shift relations with the West.
"Hopefully this can be the icing on the cake and then when the relationship between the two countries improves there can be a cherry on top where the United States will apologize for that and Iran will apologize for the hostage crisis and everybody can move on in a peaceful way," he said.
Philip J. Victor contributed to this report. With Al Jazeera and wire services.