TEHRAN -- Iran's leaders, seizing on perceived flexibility in a private letter from President Obama, have decided to gamble on forging a swift agreement over their nuclear program with the goal of ending 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, Hassan 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 on Thursday.
A senior American official did not dispute the general outlines of the letter as described by the longtime adviser and Iranian political expert, Amir Mohebbian. But the official said Mr. Obama had not promised Iran quick relief from sanctions, and had steered clear of any detailed proposal.
Mr. Mohebbian and other officials and analysts said that Iran was focused on getting quick relief from financial sanctions because they have cut it off from the international banking system, and that in exchange it might be willing to curb its 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.
The Iranian leadership was encouraged by what was described as 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. But the differing interpretations of Mr. Obama's letter in Tehran and Washington are a reminder of the political hurdles and the legacy of mistrust that both sides will have to overcome in negotiating a deal.
The American official said Mr. Obama had congratulated Mr. Rouhani on his election, and characterized the vote as an opportunity for change. But on sanctions, the official said, the Iranians were inferring relief from the president's more general pledge to resolve issues and move forward. And while Mr. Obama is open to direct talks, the official said, they will not necessarily be leader to leader.
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 returning the politically powerful military to the barracks -- for now. Those actions, along with the changed diplomatic tone, have convinced some experts that the changes are more than cosmetic.
Mr. Rouhani will present Iran's new face to world next week with an address to the United Nations General Assembly, an evening speech to the Council on Foreign Relations and the Asia Society, and a television interviews with Charlie Rose and CNN.
In an opinion essay published in The Washington Post on Friday, Mr. Rouhani said world leaders should "seize the opportunity presented by Iran's recent election."
"I urge them to make the most of the mandate for prudent engagement that my people have given me and to respond genuinely to my government's efforts to engage in constructive dialogue," he wrote.
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 the country's supreme leader, Ayatollah Ali Khamenei, proposing a new diplomatic chapter. In his reply, Ayatollah Khamenei did not take Mr. Obama up on his offer.
Their correspondence was cut short after Iran's disputed presidential election in June 2009 unleashed a popular uprising. The ensuing bloody crackdown all but snuffed out diplomacy for the next year. Mr. Ahmadinejad, re-elected as president, wrote a lengthy letter to Mr. Obama in 2010, but it did nothing to break the diplomatic ice.
This time Mr. Obama's letter found a receptive audience, which apparently, and crucially, includes for the first time Ayatollah 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.
Mr. Mohebbian, who often acts as a political commentator for foreign news media, published parts of the letter on Tuesday on one of the 20 Web sites he runs in Iran, called Secretnews.
Mr. Mohebbian said the Iranian leadership was generally receptive to the letter except for what he said was Mr. Obama's complimenting Mr. Rouhani as "the representative of the Iranian people, not of the totalitarian leaders."
This is the first time Mr. Obama has written directly to an Iranian president, and not the supreme leader, suggesting that the White House believes Ayatollah Khamenei has empowered Mr. Rouhani to seek an opening with the West.
In a sharp break with previous letter exchanges, both presidents have publicly lauded their correspondence. Mr. Rouhani said in an NBC News interview broadcast on Wednesday that the tone of Mr. Obama's letter was "positive and constructive." He added, "It could be subtle and tiny steps for a very important future."
Mr. Obama, speaking to the Spanish-language network Telemundo on Tuesday, said there were indications that Mr. Rouhani "is somebody who is looking to open dialogue with the West and with the United States, in a way that we haven't seen in the past. And so we should test it."
In his reply to Mr. Obama, Mr. Rouhani said public opinion in Iran did not favor talks, Mr. Mohebbian said. Iran's president urged Mr. Obama to "prepare the grounds for successful negotiations" with a gesture of good faith.
The American official said that while Mr. Rouhani was frank about policy differences with the United States, his letter, too, had a different tone -- less the list of grievances that he said characterized letters from Ayatollah Khamenei or Mr. Ahmadinejad.
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.
"It is the leader who decides on the possibility, scope and extent of potential talks with the U.S.," Mr. Mohebbian said. He emphasized that Ayatollah Khamenei was in excellent health, "but we need him to reach consensus within our system."
"He feels this is the moment to try and solve this problem."
The leadership is also desperate to escape the withering financial sanctions imposed in recent years, particularly the ban on Iranian money transfers through the Swift system. It can live without oil sales, analysts have said, but not without the ability to transfer money.
Mr. Mohebbian said Iran is hoping that the White House will lift some sanctions as a gesture to show its seriousness about the talks. "We particularly want to be readmitted to the Swift system," he said.
He and other analysts warned that while Iran's political establishment fully agreed that talks were worth trying, the consensus could break down within months if there were no results.
"The world must know that time is not unlimited for solving the nuclear problem," Mr. Rouhani said in his first live television interview on Iranian state television, on Sept. 10.
At the White House, where Mr. Obama has long sought a rapprochement with Iran but been repeatedly frustrated, officials share the sense that this time may be different.
"Rouhani is sending signals he wants to deal," said Dennis B. Ross, a former adviser to Mr. Obama on Iran. "He wants to end the sanctions and knows he does not have a lot of time to deliver -- Iranian presidents have some space in their first year and then it declines."
Thomas Erdbrink reported from Tehran, and Mark Landler from Washington.
This article originally appeared in The New York Times.