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. 
 
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 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. 
 
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 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. 
 
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 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. 
 
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 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. 
 
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 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. 
 
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 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. 
 
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 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.” 
 
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 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. 
 
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 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. 
 
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 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. 
 
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 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. 
 
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 “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. 
 
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 “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. 
 
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 “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.” ||||| Story highlights The call lasted 15 minutes, Susan Rice tells CNN 
 
 She characterized it as "cordial and constructive" 
 
 Rouhani's tweets reflected tone of conversation, White House official says 
 
 Rouhani tweets the conversation about nuclear negotiations 
 
 U.S. President Barack Obama spoke by telephone Friday with Iranian President Hassan Rouhani -- the first direct conversation between leaders in Washington and Tehran since 1979 -- raising the possibility a deal can be reached over Iran's controversial nuclear program. 
 
 Describing the conversation as a starting point, Obama said he believes an agreement is possible regarding Iran's nuclear ambitions that could lead to better relations. 
 
 "While there will surely be important obstacles to moving forward and success is by no means guaranteed, I believe we can reach a comprehensive solution," Obama told reporters during a White House briefing. 
 
 Western leaders have expressed cautious optimism about Iran's more moderate tone under Rouhani, whose recent comments have raised hopes that a deal could be struck over the Middle Eastern nation's nuclear program. 
 
 Obama said he reiterated to Rouhani statements he made earlier in the week during the United Nations General Assembly, where he signaled the United States was open to negotiations with Iran provided real action is taken. 
 
 JUST WATCHED Iranians praise contact with U.S. Replay More Videos ... MUST WATCH Iranians praise contact with U.S. 01:37 
 
 "So the test will be meaningful, transparent, and verifiable actions, which can also bring relief from the comprehensive international sanctions that are currently in place," he said Friday. 
 
 The conversation between the two men came at the end of the General Assembly, where conjecture abounded over whether Obama and Rouhani would meet in person and what that might mean for U.S.-Iranian relations. 
 
 Rouhani told reporters Friday that there wasn't enough time to plan such a face-to-face meeting. 
 
 The last time a U.S. president spoke with an Iranian leader was in 1979, when Jimmy Carter talked by telephone with Shah Mohammed Reza Pahlavi before Pahlavi was overthrown. 
 
 National Security Advisor Susan Rice told CNN's Fareed Zakaria that the administration was contacted by the Iranian delegation. 
 
 "Today, somewhat surprisingly, we were contacted by them to say that President Rouhani would like to speak to President Obama on the telephone on his way out of town, and we were able to make that call come together and it was a constructive conversation," she said. 
 
 The call lasted about 15 minutes, with translation, Rice said. 
 
 Rice characterized the call as "cordial and constructive." 
 
 The news of the conversation played out on Twitter in posts by Rouhani, who recounted his conversation with Obama just minutes before the American president spoke with reporters at a White House briefing. 
 
 A senior Obama administration official said Rouhani's tweets reflected the tone of the telepone conversation between the two leaders. "We'll continue to watch his Twitter feed," the official, speaking on condition of anonymity, said. 
 
 According to Rouhani's posts, Obama told the Iranian president that he was "convinced relations between Iran and US will greatly affect the region." 
 
 "@BarackObama to @HassanRouhani If we can make progress on #nuclear file, other issues such as #Syria will certainly be positively affected," the president said in a follow-up message. 
 
 Rouhani responded, according to his tweet: "In regards to #nuclear issue, with political #will, there is a way to rapidly solve the matter." 
 
 He also told Obama, according to his Twitter post, he was hopeful about upcoming meetings on the issue between representatives of Iran and the permanent members of the U.N. Security Council -- the U.S., China, Russia, Britain and France -- as well as Germany. 
 
 "@HassanRouhani to @BarackObama: I express my gratitude for your #hospitality and your phone call. Have a good day Mr President," Rouhani said in post on Twitter. 
 
 Earlier, Rouhani told reporters he was heartened by Thursday's meeting between U.S. Secretary of State John Kerry and Iranian Foreign Minister Mohammad Javad Zarif as part of a meeting between Iran and the six countries trying to tackle international concerns about Iran's nuclear program. 
 
 It was the first face-to-face meeting between such high-level officials of the two countries in more than 30 years. 
 
 Obama and Rouhani both indicated that the talks between Kerry and Zarif will continue at the so-called P5+1 meeting, which brings together representatives of the five permanent member states of the United Nations and Germany with emissaries from Iran over Tehran's nuclear program. 
 
 "Throughout this process, we will stay in close touch with our friends and allies in the region, including Israel," Obama told reporters, acknowledging concerns such talks are likely to raise with Israeli leaders. 
 
 Obama acknowledged that after 35 years of mistrust, "a path to a meaningful agreement will be difficult and at this point both sides have significant concerns that will have to be overcome." 
 
 "But I believe we have a responsibility to pursue diplomacy, and that we have a unique opportunity to make progress with the new leadership in Tehran," he said. 
 
 Western leaders have said Iran seems to sound different under the leadership of Rouhani, who replaced Mahmoud Ahmadinejad as president this summer. On Friday, it was Rouhani's turn to return the compliment, saying European Union officials and Obama sound "different compared to the past." 
 
 Rouhani told reporters Friday his election helped pave the way for better relations between the Iran and the West, which has imposed heavy sanctions on the country. He also said Iran wants quick resolution to the nuclear issue. Western leaders believe the country's nuclear program is designed to produce weapons. Iranian leaders have said it is purely peaceful. 
 
 "I assure you that on the Iranian side, this will is there fully, 100%, that within a very short period of time, there will be a settlement on the nuclear issue," he told reporters. ||||| Foreign ministers from the five permanent members of the U.N. Security Council and Germany will meet with Iran's top diplomat on Thursday to test the Islamic Republic's apparent willingness to reach a deal to resolve international concerns about its nuclear program after years of defiance. 
 
 Iranian Foreign Minister Mohammad Javad Zarif, left, and French Foreign Minister Laurent Fabius shake hands before conducting a bilateral meeting during the 68th session of the United Nations General... (Associated Press) 
 
 The meeting on the sidelines of the annual United Nations General Assembly is aimed at paving the way for the first round of substantive negotiations on the nuclear issue since April, probably next month. It will also mark the highest-level, direct contact between the United States and Iran in six years as Secretary of State John Kerry comes face-to-face with Iranian Foreign Minister Javad Zarif. 
 
 The United States, Britain, France, Russia, China and Germany will participate with European Union foreign policy chief Catherine Ashton serving as host of the meeting. 
 
 Encouraged by signs that new Iranian President Hasan Rouhani will adopt a more moderate stance than his hard-line predecessor but skeptical that the country's supreme leader will allow a change in course, President Barack Obama directed Kerry to lead a new outreach to explore possibilities for resolving the long-standing dispute. However, Obama and other U.S. officials have said Iran must prove its commitment with actions, not just words. 
 
 Rouhani is in New York this week, making his debut on the world stage with an address to the General Assembly and a series of other speeches, news conferences and bilateral meetings. 
 
 During his visit, Iran has shown new urgency in reviving the stalled negotiations, seeking to ease crippling international sanctions as quickly as possible. Rouhani said Wednesday that "we have nothing to hide" and Zarif said he hoped his counterparts "have the same political will as we do to start serious negotiations with a view to reaching an agreement within the shortest span of time." 
 
 The West suspects Iran is trying to build a nuclear weapon and has imposed crippling sanctions on Tehran that have slashed its vital oil exports and severely restricted its international bank transfers. Inflation has surged and the value of the local currency has plunged. 
 
 Tehran has repeatedly denied that its nuclear program is for anything other than peaceful purposes. 
 
 But since his June election, Rouhani has made clear he is seeking relief from the sanctions and has welcomed a new start in nuclear negotiations in hopes this could ease the economic pressure. He has said he has the full support of Iranian Supreme Leader Ayatollah Ali Khamenei, who has the final word on all important matters of state including the nuclear question. 
 
 "If there is political will on the other side, which we think there is, we are ready to talk," Rouhani told editors Wednesday in New York. "We believe the nuclear issue will be solved by negotiation." 
 
 In his speech to world leaders at the U.N. on Tuesday, Rouhani repeated Iran's long-standing demand that any nuclear agreement must recognize its right under international treaties to continue enriching uranium. The U.S. and its allies have long demanded a halt to enrichment, fearing Tehran could secretly build nuclear warheads. 
 
 Uranium enriched to low levels can be used as fuel for nuclear energy but at higher levels of enrichment, it could be used to build a nuclear weapon. 
 
 Rouhani also insisted in his speech that any deal be contingent on all other nations declaring their nuclear programs too are solely for peaceful purposes _ alluding to the U.S. and Israel. 
 
 Iran watchers say Rouhani may have limited time to reach a settlement _ possibly a year or less _ before Khamenei decides negotiations are fruitless. That may explain Zarif's call to reach a deal in the short time span. 
 
 "He is not negotiating for the sake of negotiating and dragging it out," Haleh Esfandiari, director of the Mideast program at the Wilson Center think-tank in Washington, said of Rouhani. "His reputation, and the country's reputation, is at stake. This is an issue they are willing to work on, and move to take concrete steps to serious negotiations." 
 
 Rouhani in New York has come across as a more moderate face of the hard-line clerical regime in Tehran. In particular, he appears to be trying to tone down the caustic rhetoric of his predecessor, Mahmoud Ahmadinejad, with regard to Israel _ one of the points of friction in relations with the West. 
 
 Still his speech to the U.N. was peppered with Iran's traditional digs at America and the West _ a reminder that a diplomatic warming will not come quickly or easily. 
 
 Rouhani condemned "the Nazi massacre against Jews, Christians and others" in his remarks to editors on Wednesday. 
 
 "There is no way to ignore Nazi crimes against Jews," he said. But he added "it is important that those victimized not seek compensation by victimizing other groups" _ a pointed reference to what he has described as Israel's occupation and subjugation of Palestinians. 
 
 Citing the Quran, or Muslim holy book, Rouhani said that if any innocent person is killed, it is as if all of mankind has been killed." 
 
 Ahmadinejad, in contrast, once called the Holocaust a "myth" and later said more research was needed to determine whether it had really happened. 
 
 Israel's U.N. delegation walked out of Rouhani's speech Tuesday in protest. But in a text message statement sent to reporters on Wednesday, Finance Minister Yair Lapid said Prime Minister Benjamin Netanyahu's instruction to Israeli delegates to walk out was a "mistake." He said it created the impression that Israel was not interested in encouraging a peaceful solution to Iran's suspect nuclear program. 
 
 Rouhani said Iran must be careful in starting a new relationship with the U.S. after three decades of frozen ties, adding that his first goal is to reduce the distrust. He noted that there are radical voices in America and radical voices in Iran who would not like to see that happen, but said that the voices of moderation need to be strengthened and supported. 
 
 "The more two countries are apart, the more suspicions, fears and miscalculations creep in," he said in remarks that were initially supposed to be off the record. However, in response to requests from journalists, Rouhani agreed some of his remarks could be quoted. 
 
 He said he has no problem shaking hands with President Barack Obama. But he said he thought the first meeting between leaders of their two countries in more than three decades needed to be handled very carefully. There had been heated speculation that the two might meet at the U.N. on Tuesday and even exchange handshakes and pleasantries. But that did not happen. 
 
 The White House said Obama remains open to the possibility of an informal encounter with Rouhani at a future date. 
 
 ___ 
 
 Associated Press reporters John Daniszewski and Bonny Ghosh in New York and Ali Akbar Dareini in Tehran, Iran, contributed to this report. 
 
 Follow Lara Jakes on Twitter at: https://twitter.com/larajakesAP
– Iran thinks it's poised to finally bury the hatchet with the US and strike a sanctions-ending nuclear deal—because officials believe President Obama offered that kind of rapprochement in his letter to newly-elected moderate Hasan Rouhani, a top Iranian adviser tells the New York Times. In Iran's reading, Obama offered face-to-face talks and promised to lift sanctions if Rouhani demonstrates a willingness to "keep your commitments and remove ambiguities." But Washington's interpretation is much less dramatic; an official says Obama wasn't necessarily promising leader-to-leader talks, or any specific sanction action. Rouhani wants to strike a quick deal in the next six months, before parliamentary elections begin. The normally politically powerful military is currently defanged, and Ayatollah Khamenei appears to be on board. In the meantime Rouhani's on a charm offensive. He wrote an op-ed in today's Washington Post in which he offers to "help facilitate dialogue between the Syrian government and the opposition," and promises an attempt to "move beyond impasses" with regard to Iran's nuclear program. He's on the interview circuit as well, with one coming up with Charlie Rose. Next week he'll give his first UN address, and for once the US may not walk out, the Post reports. Obama is speaking the same day, so the two might even meet.