In a month since taking office, Iran's President Hassan Rouhani has signalled a sharp departure from the foreign policy and the tone of his predecessor.
The eagerness of his administration to break away from eight years of Mahmoud Ahmadinejad's bombastic pronouncements was apparent three weeks ago when the new foreign minister wished Jews a "Happy Rosh Hashanah" before asserting that Iran had never denied the Holocaust, adding: "The man who was perceived to be denying it is now gone."
Mr Rouhani has also exchanged "positive" letters with US President Barack Obama, and told the US broadcaster NBC that Iran wants to engage with the world and not develop nuclear weapons.
He has even become the first Iranian president to pen an op-ed in a US newspaper. Writing in the Washington Post last week, he called for "constructive" interaction with other countries and declared Iran's readiness to help end the conflict in Syria.
The message President Rouhani is trying to convey is clear - that he has "complete authority" and "sufficient political latitude" to engage with the US and its allies on the substance of their concerns.
Gary Sick, a former White House National Security Adviser, told the BBC: "What we have seen already has been such a dramatic shift. Rouhani and his team are the 'anti-Ahmadinejad'.
"The sound of the rhetoric makes it so much easier for an American president to react positively.
"The positive tone was evident in Obama's interview with TeleMundo TV. President Rouhani's overtures are of the kind we have not seen before and we should test it."
The talk of an "accidental" meeting between the two presidents in the halls of the UN's headquarters this week has gone from wishful thinking to a real possibility.
The mood in New York is also very different from the previous years.
Gone are the protests and annual adverts on TV and billboards on Times Square with big pictures of Mr Ahmadinejad, denouncing his anti-Israel rhetoric and warning about Iran's nuclear programme.
Instead, diplomats are waiting with anticipation to see how the new president gets Iran out of the international relations mess he has inherited from Mr Ahmadinejad.
There is little doubt that Mr Rouhani's talk of co-operation with the world has put sceptics in the US on the defensive.
Opponents of US-Iran dialogue cannot keep up with the flurry of interviews, tweets and positive signals thrown out by Mr Rouhani and his media team.
But the Iranian charm offensive brings to light two critical questions - can Mr Rouhani turn his words into deeds, and is Washington ready to make a deal with Tehran?
Robert Einhorn, a former state department special adviser for non-proliferation and arms control who was part of the US negotiating team at talks between world powers and Iran, says: "I believe Obama administration is prepared to address Iran's concerns very seriously and flexibly provided that the administration sees real movement on the Iranian side."
"Under Ahmadinejad, the perception in Washington was that Iran wasn't really interested in a deal. That has changed. I think the administration believes there is a real opportunity here."
Five years into Mr Obama's presidency, have the stars finally aligned for constructive US-Iran talks? Many believe so.
The opportunity at hand is largely the result of the Iranian election, in which Mr Rouhani's surprise victory ushered in the same moderate politicians who prior to the Ahmadinejad era had agreed to suspend Iran's uranium enrichment programme and helped the US defeat the Taliban in Afghanistan.
The White House, however, tends to view Iran's new openness as a sign that sanctions have worked.
However, that assessment may miss the important changes taking place in Iran and tempt Washington to push for even more sanctions to elicit even greater Iranian flexibility.
"There is a temptation in Washington to believe that no positive step is taken unless the US issues a threat, takes military action or imposes sanctions," a European diplomat at the UN said.
In conversations with the Iranian side, it is clear they have doubts about whether the US is ready to take nuclear diplomacy to a new level.
Iranian nuclear concessions will likely only be offered - even by Mr Rouhani - if Mr Obama puts significant sanctions relief on the table.
If that is not forthcoming, Iranian hardliners will be able to attack the president for offering too much for no tangible reward.
They denounced him as a traitor in 2003 when, as Iran's top nuclear negotiator, he agreed to the suspension of Iran's uranium enrichment activities without gaining any US concessions.
But Mr Rouhani is unlikely to once again offer the West anything on credit.
The problem is that some of the most hard-hitting sanctions can only be lifted by the US Congress.
It remains to be seen whether Mr Obama has what it takes to neutralise Congress in the same way in which Mr Rouhani appears to have temporarily pacified Iran's parliament. The week ahead at the UN will provide some clues.
What is for certain is that millions of Iranians will be watching proceedings in New York for reactions to the president they elected into office, despite all odds, to see if both he and their country's opponents seize the moment and find a peaceful resolution to their dispute.