Iranian president Hassan Rouhani and his U.S. counterpart speak over the phone, a first in 34 years.

The Iranian president, his car making its way to the airport through New York’s dense traffic, gets in touch with the White House Situation Room. President Barack Obama, at his desk in the Oval Office, gets on the phone. Fifteen minutes later, the two say goodbye in each other’s language.

And with that, a generation-long rift between the U.S. and Iran is that much closer to being bridged.

Iranians awoke on Saturday to learn that their president, Hassan Rouhani, had spoken directly to President Barack Obama, breaking through a barrier that had left American and Iranian presidents divorced from such contact for 34 years. The two presidents pledged to resolve concerns about Iran’s nuclear ambitions, which have isolated Iranians from the global community and led to crippling economic sanctions.

The appetite for serious talks having been tested at a presidential level, the focus turns to negotiations among foreign ministers and other officials from the five permanent members of the U.N. Security Council plus Germany, who together will chart a path forward, a senior Obama administration official said. The group wants Iran to present a more detailed proposal before or at the next round of negotiations, scheduled in Geneva on Oct. 15-16, another U.S. official said.

Mr. Rouhani’s aides initially reached out to arrange the call, said officials, who weren’t authorized to comment by name and demanded anonymity. But it was Mr. Obama who signalled days earlier he was willing to meet with his Iranian counterpart. By the end of the call, Mr. Obama was suggesting that a breakthrough on the nuclear issue could portend even deeper ties between the U.S. and Iran a notion that would have seemed unfathomable in recent years, when Mr. Rouhani’s predecessor was describing America in satanic terms.

The telephone call capped a week of seismic shifts in the relationship while Mr. Rouhani was in the U.S. for an annual U.N. meeting. Mr. Obama had left open the possibility of an exchange with Mr. Rouhani, but the Iranian later said the timing wasn’t right.

But hours before the phone call, at a news conference in New York, Mr. Rouhani linked the U.S. and Iran as “great nations.” And the night before, U.S. and European diplomats were hailing a “very significant shift” in Iran’s attitude and tone in the first talks on the nuclear standoff since April.

“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,” Mr. Obama told reporters on Friday at the White House.

The stunning shift in tone aside, there was immediate scepticism that Iran was cynically seeking to procure relief from blistering economic sanctions but would not take concrete action to assuage global concerns that it is seeking to build nuclear weapons.

The U.S. and Western allies imposed the sanctions after years of stonewalling inspections and secrecy about its activities fuelled fears about its intentions especially as they relate to Israel, a staunch U.S. ally and the target of much of Iran’s most fiery rhetoric. Iran insists its nuclear programme is strictly for peaceful purposes.

For Obama, the call marked a realization of sorts of a stance he took in 2008, when he was first running for president and saying he would be willing to meet with leaders from so-called rogue nations like Iran, Syria and North Korea without preconditions. The policy earned him rebukes from critics who questioned what they derided as a Pollyanna approach to security threats.

Five years later, the man behind the White House podium was otherwise deeply ensnared in a dysfunctional stalemate with lawmakers over spending and health care. Announcing the diplomatic leap forward, Mr. Obama sought solace in foreign policy as he condensed the hopes and challenges of what remains of his presidency from historic outreach to Iran, to budding progress on Syria’s chemical weapons, to the untidy work of dealing with Congress.

The offer on the negotiating table for Mr. Rouhani would give Iran some sanctions relief and pledge not to impose new penalties in exchange for ending uranium enrichment that nears or reaches 20 per cent, a level just a few steps from what’s needed to produce fuel for an atomic weapon. The deal, offered last February, would also require suspended enrichment at Iran’s fortified underground Fordo facility and increased access for U.N. inspectors.

Mr. Obama said that the U.S. will coordinate closely with its allies including Israel, which considers a nuclear-armed Iran to be an existential threat. Officials also said the U.S. had informed Israel about the call with Mr. Rouhani.

Israel’s lingering doubts that Iran’s overtures are anything more than a stall tactic will be on display next week, when Mr. Obama meets with Israeli Prime Minister Benjamin Netanyahu at the White House.

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