President Hassan Rowhani appears to be keeping campaign pledges of broader domestic freedoms, a week before heading for New York as he seeks to rebuild Iran's tarnished international image.
His overtures have sparked a welcome response from the White House and from UN chief Ban Ki-moon but a predictable cold shoulder from Benjamin Netanyahu, prime minister of Tehran's arch foe Israel.
A moderate by Iran's political standards, mid-ranking cleric Rowhani won a surprise victory in the Islamic republic's June presidential election.
He campaigned on relaxing social and cultural intolerance at home, engaging constructively with the international community and also on shoring up Iran's sanctions-hit economy.
Reports on Wednesday of the release of nearly a dozen political prisoners, including high-profile figures, came as Rowhani gave his first interview to an American news channel.
Speaking to NBC News, he reached out to long-time foe the United States by praising a recently received letter from his American counterpart Barack Obama, calling it "positive and constructive."
That rare compliment was the latest signal in a cautious game of diplomatic rapprochement in recent weeks as Tehran and Washington -- deadlocked over several key issues including Iran's controversial nuclear ambitions -- appear to be seeking to resolve their differences.
On Tuesday, Obama vowed to test the sincerity of signs that Rowhani may be ready for productive talks on Iran's nuclear activities, which Western powers and Israel suspect have a military aim despite repeated denials.
And on Thursday, White House spokesman Jay Carney said "there have been a lot of very interesting things said out of Tehran and the new government, and encouraging things.
"There's no question that the new Iranian government has been taking a different approach in the things that it has said about a lot of issues."
In his NBC interview, Rowhani pledged Tehran would never seek to acquire atomic weapons, while insisting there was "sufficient political latitude" in Iran to resolve the nuclear showdown.
He was referring to a statement by Iran's supreme leader Ayatollah Ali Khamenei -- who has the final say on the nuclear drive -- that sometimes "heroic flexibility" was necessary in diplomacy.
This was interpreted as providing Rowhani with more latitude in future nuclear talks.
Rowhani will leave for New York on September 22 to attend the annual United Nations General Assembly.
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He is expected to use his speech there to announce Iran's desire to repair its relations with the West, heavily strained under his hardline predecessor Mahmoud Ahmadinejad.
Foreign Minister Mohammad Javad Zarif, already in New York, is scheduled to meet EU foreign policy chief Catherine Ashton on how to take forward decade-long talks on Tehran's nuclear project.
Ban, speaking on Thursday after meeting Zarif, praised Tehran for releasing the political prisoners and promoting dialogue with the international community.
He said he told Zarif he was pleased Iran "is now taking some concrete steps to fulfil the promises made by President Rowhani during his recent election campaign."
But Netanyahu warned the world "not to let itself be duped by the untrustworthy declarations of the Iranian president."
"This same Rowhani has deceived the international community in the past" in discussions over the country's disputed nuclear programme," an apparent reference to the time when he was Tehran's chief nuclear negotiator.
The release of the political prisoners, including prominent human rights lawyer Nasrin Sotoudeh, diplomat and founder of a main reformist party Mohsen Aminzadeh and reformist politician Feyzollah Arabsorkhi, was welcomed by media and pundits in Iran.
"I truly hope Mr Rowhani will resolve all the issues, one by one," analyst Sadeq Zibakalam told the reformist Shargh daily.
A Western diplomatic source told AFP the release showed "Rowhani really wants to keep the promises he made during the campaign, and that his message of moderation is also credible."
The source added that Rowhani "has now very cautiously opened the door for the release of high-profile cases", including opposition leaders Mir Hossein Mousavi and Mehdi Karroubi, who have been under house arrest since February 2011.
However, the fate of Mousavi and Karroubi is a sensitive topic that could antagonise hardline conservatives, who held almost complete sway within the regime during Ahmadinejad's tenure.
But for now, Rowhani appears to have the backing of the nation's ultimate authority.
"For the moment he has the backing of Khamenei," the Western source said, adding that there was a political battle being waged behind scenes.
Khamenei on Tuesday threw his support behind Rowhani by urging the elite Revolutionary Guards to stay out of politics,endorsing an appeal by the president to the hardline organisation.
"We are seeing that consensus is being achieved on higher levels" on key issues, analyst Saeed Leylaz told Shargh.