The report, available on the WikiLeaks website Tuesday, also suggested Iran trusted its arch-foe the United States more than ally Russia to follow through with the U.N.-backed proposal: providing reactor-ready fuel in exchange for Iran giving up control of its low-enriched uranium stockpile.
The assessment was given to a top U.S. envoy by Turkish Foreign Minister Ahmet Davutoglu, whose nation has a growing friendship with Tehran and is scheduled to host the next round of nuclear talks later this month between Iran and six world powers, including the United States.
The fuel swap proposal is a centerpiece of efforts for greater international controls on Iran's nuclear program, which the West and others fear could lead to development of atomic weapons. Iran insists it only seeks reactors for power and research.
The U.N. plan in 2009 called for Iran to ship its low-enriched uranium out of the country and receive nuclear fuel ready for use. Iran balked at the proposal and outlined alternative fuel swaps involving allies Brazil and Turkey. But the six nations - the five permanent U.N. Security Council members plus Germany - said the offers fell short of their demands.
In late 2009, Davutoglu told visiting Assistant Secretary of State Philip Gordon that Iran's government was willing to work out some kind of fuel swap arrangement, but Ahmadinejad was facing "huge pressures" at home, according to the secret memo.
Davutoglu was quoted as saying that the proposal deal was "interpreted by some circles in Iran as a virtual defeat" by Western pressures.
The cable said Turkish officials had asked Ahmadinejad "if the core of the issue is psychological rather than substance."
"Ahmadinejad had said 'yes,' that the Iranians agree to the proposal but need to manage the public perception," the message said, adding that Turkish officials consider Ahmadinejad as "more flexible than others who are inside the Iranian government."
It also noted that it appears the Iranians have "more trust" in the U.S. envoys than British negotiators and "the Iranians would also prefer to get fuel from the U.S. rather than the Russians."
The talks between Iran and the world powers resumed in Geneva last month after an impasse lasting more than a year.
Iran pressed hard to have the second round in Turkey, which has developed close economic and political ties with Iran.
The leaked cable said the U.S. diplomat Gordon noted that Washington believes Turkey can be "helpful as a mediator" with Iran, but he also pushed for a stronger Turkish stance on Iran's nuclear efforts.
It quoted the Turkish foreign minister as replying: "Only Turkey can speak bluntly and critically to the Iranians ... but only because Ankara is showing public messages of friendship."