TEHRAN, Iran -- Iran's leaders seized on perceived flexibility in a private letter from President Barack Obama and have decided to gamble on forging a grand bargain over their nuclear program to end crippling sanctions, a prominent adviser to the Iranian leadership said Thursday.
The adviser, who participated in top-level discussions of the country's diplomatic strategy, said that Mr. Obama's letter, delivered to Iran's new president, Hasan Rouhani, about three weeks ago, promised relief from sanctions if Tehran demonstrated a willingness to "cooperate with the international community, keep your commitments and remove ambiguities." The text of the letter has not been made public, but the adviser described its contents in an interview in his office Thursday.
The adviser and other officials and analysts said Iran was focused on getting quick relief from financial sanctions that have cut it off from the international banking system, possibly in exchange for curbs on the Iranian nuclear enrichment program. Some in the leadership are also worried that, if nuclear talks do not yield quick results, Iran's hard-line clerics and military men -- currently sidelined -- could attack Mr. Rouhani as a sellout and clip his political wings.
A senior U.S. official did not dispute the general outlines of the letter as described by Amir Mohebbian, an Iranian political expert and longtime adviser to Iran's supreme leader, Ayatollah Ali Khamenei. But the official said Mr. Obama had not promised Iran quick relief from sanctions, insisting that they would be lifted only as a result of negotiations over Iran's nuclear activities.
The Iranian leadership was encouraged by what they said was Mr. Obama's offer to conduct face-to-face talks, which they prefer to the more bureaucratic and lengthy negotiating process with a group of five major world powers, Mr. Mohebbian said.
The one-and-a-half-page letter, which the Iranian president answered with a letter of similar length, has kindled hopes that the international charm offensive Iran began after Mr. Rouhani's election in June may produce a genuine diplomatic breakthrough. .
The U.S. official said Mr. Obama had congratulated Mr. Rouhani on his election, and characterized the vote as an opportunity for change. But the official was adamant that Mr. Obama had made no promises about immediate, or even quick, relief from the sanctions.
The Iranians, he said, were inferring that from the president's general pledge to resolve issues and move forward.
The Iranian reaction to the letter provides critical insight into a decisive and unexpected shift in strategy by the moderate new president as Iran struggles to restore vitality to its economy and undo years of hostile relations with most of the world under the former president, Mahmoud Ahmadinejad.
The overtures to the United States are part of a flurry of steps altering the trajectory of the Iranian state, including domestic liberalizations and the return of the politically powerful military back to the barracks -- for now. Those concrete actions, along with the changed tone of its diplomacy, have convinced some analysts that the changes are more than cosmetic.
Mr. Rouhani will present Iran's new face to world next week with an address to the U.N. General Assembly, an evening speech to the Council on Foreign Relations and the Asia Society, and a television interview with Charlie Rose.
Skeptics were quick to point out that Mr. Obama has reached out to Iran before. Having promised as a candidate to extend an olive branch to old enemies, he sent a letter early in his first term to Ayatollah Khamenei, proposing a new diplomatic chapter. Ayatollah Khamenei sent a reply but failed to take Mr. Obama up on his offer.
This time Mr. Obama's letter found a receptive audience, which apparently, and crucially, includes for the first time Mr. Khamenei. Mr. Mohebbian said he had been present at an official meeting of the leadership at which the letter was read aloud and discussed by someone from "the highest levels" of Iran's political establishment, terminology that usually describes the office of the supreme leader.
Iran's leaders are apparently convinced that the next six months, before campaigning begins for parliamentary elections in March, represent the best opportunity to reach a nuclear agreement in over a decade, Mr. Mohebbian said.
The leaders considered the tone of Mr. Obama's letter a very promising sign, and paradoxically, they view what they see as America's declining regional influence as a positive. Mr. Rouhani has publicly applauded Mr. Obama's decision to refrain from striking Syria for its poison gas attack on its own civilians.
Mr. Mohebbian said Ayatollah Khamenei had been growing concerned about the future of the revolution, with so many of its founders aging. In particular, he wants to settle the nuclear issue and ease tensions with the United States.