Somewhere in the bowels of the United Nations building in New York this week, away from journalists and cameras, Barack Obama may shake the hand of Hassan Rouhani. It won’t be in anyone’s diary, there’ll be no statements or photo ops, but the meeting of the presidents of the United States and Iran — the first time that’s happened since Jimmy Carter in the 1970s — will be momentous.

Unlike North Korea, a now seemingly intractable, nuclear-fuelled diplomatic stalemate, Iran might be able to be pulled back from the brink under Rouhani’s leadership. Rouhani will address the UN in a speech likely to veer sharply away from the stance of hardline predecessor Mahmoud Ahmadinejad. Foreign Minister Mohammad Javad Zarif has already met British diplomats; UK Foreign Secretary William Hague declared afterwards: “We don’t want a confrontational relationship with Iran.”

Mohammad Khatami, a former Iranian president and the leader of the country’s revived reformist movement, says the West can trust Rouhani — or at least has to. He writes in an op-ed for The Guardian today:

“President Rouhani’s government was elected by a society seeking positive change, at a time when Iran and the wider region was desperately in need of prudence and hope. This vote was not limited to a specific political camp; as well as many reformers, many political prisoners and a significant body of conservatives had a share in Rouhani’s victory. For the first time there is an opportunity to create a national consensus above and beyond partisan factionalism – one that may address the political predicaments of the country, with an emphasis on dialogue and mutual understanding globally.

“Explicit public support from the supreme leader of the Islamic republic provides Rouhani and his colleagues with the necessary authority for a diplomatic resolution of a number of foreign policy issues with the West, not just the nuclear issue.”

It could all start with a handshake. Diplomacy is a wonderful thing.