The long slog of diplomacy with Iran—a pariah nation since its 1979 revolution—was always about more than the bomb. It was about the return of the world’s eighteenth-largest country—and its vast military, population, and consumer base—at a time when the Middle East is crumbling. A nuclear deal could alter the regional dynamics. The chaos in the Middle East and the rise of the Islamic State, which has come within twenty-five miles of Iran’s borders, have redefined the dangers to Iran, as well as its priorities. During the nuclear talks in Vienna, Iran’s foreign minister, Javad Zarif, released a YouTube message to the West, in English, about how a deal could “pen new horizons to address important, common challenges.” Even Iran's Supreme Leader, Ali Khamenei, amid his customary anti-American bombast, offered a tantalizing remark. “If the other side gives up its usual diversionary tactics,” he told a group of poets, in April, “this will become an experience for us that, very well, we can negotiate with them on other issues.” Throughout the spring, Tehran was abuzz over the prospect of coöperation with the United States.

During the final weeks of negotiations, I spoke to Zarif in Tehran about Khamenei’s statement and how a deal might impact other conflicts in the world’s most volatile region.

So what does the day the deal is signed look like?

The Leader said that, if the United States shows that it is serious, that it is willing to abandon the language of coercion and threat, and is prepared to deal with Iran with mutual respect as far as the nuclear issue is concerned, then we will consider other options. That is an extremely important offer that’s on the table. ...

The day after a deal, it will be a lot of work for a lot of people to get it implemented. And it’s a huge process, both in Iran and, particularly, in the United States, because some people have been accustomed to the sanctions. … Bureaucracies have been formed, careers have been advanced. And then we hope that will remove, in my view, a smokescreen that enabled many to hide the real problems in our region. … And we and our neighbors in the region will move in a coöperative way to deal with the real issues.

When you talk about the real issues in the region, what do you mean?

I’m talking first and foremost about extremism and terrorism, which is a menace in the region that threatens everybody. We see that Daesh [the Islamic State] is spreading its influence in spite of all the efforts. … Sometimes countries in the region have even helped promote the underlying causes for attraction of new recruits to these organizations.

Sectarianism is a challenge first and foremost for every government in this region, but also a global challenge, because the wider global implications of violent sectarianism are extremely difficult to predict now. … The only way of dealing with them is regional coöperation, not just on a political level but cultural, educational, and people-to-people contacts, which are unfortunately not on the rise but diminishing.

How does a nuclear deal change Iran?

Well, it will provide for greater interaction and greater integration. … You cannot enhance confidence through isolation. Isolating people will push them to be distrustful and will push you to be distrustful of the other side, and that entrenches the concept of “enemy.” So that’s, in my view, the most important gain.

I don’t expect, all of a sudden, a revolution in a different situation. We will have more trade; we will have less United States interference in our trade with other countries. Iran is a huge investment opportunity, and the human resources in Iran are probably second to none in this region. The pool of educated, serious, hardworking labor force in Iran is probably the best in the region. … This is the most stable place in the neighborhood. So it is an opportunity. A lot of people are already interested to come to Iran.

But that perspective, while appealing, is not a panacea. We need to make adjustments, and sanctions have enabled us to make some of those adjustments, moving away, to the extent possible, from a rentier economy to a more serious economy, which would not have been possible without the sanctions or without the drop in oil prices. So some of these are blessings in disguise.

You said to me eighteen months ago that your next priority after a nuclear deal would be improving relations, particularly in the Gulf.

The Persian Gulf: that has always been my priority, not after a nuclear deal. … My first trip outside Iran was to this neighborhood. Iran can only prosper in a stable and prosperous neighborhood. For us, security in both the Central Asian and Caucasus region, as well as in the Persian Gulf region and in Turkey, Pakistan, and Afghanistan, is extremely important.

I’m interested in how you close the gap with Saudi Arabia—the major Sunni power, the guardian of Islam’s holy places—at a time when rhetoric is reaching unprecedented levels. It’s not just about Yemen.

It’s about Iraq. It’s about financing Al Qaeda. It’s about financing the Taliban. It’s about financing Daesh. It’s about financing al-Nusra. It’s about creating all sorts of havoc in this region. So it’s not just about Yemen; it’s about financing terrorist organizations that are abducting Iranian civilians and are killing Iranian diplomats in Beirut, in eastern Iran. It’s about all sorts of shortsighted, panicking activities that these people are engaged in.

Let me play devil’s advocate. The current foreign minister of Saudi Arabia was the target of an assassination plot, according to a U.S. court.

Well, according to many U.S. courts, we were behind 9/11. Nineteen Saudi and Emirati citizens were killed in action. … There are many court cases from New York and from Washington where Iran has been ordered to pay restitution for being part of the 9/11 plot. So the U.S. courts are not, for me, the best measure of reality.

Do you see a time when you and the new Saudi foreign minister, Adel al-Jubeir, will sit down and have a constructive conversation about coöperation and mutual interests in the region?

Why not? I have no problem in sitting down with anybody from this region, provided they are not engaged in acts of criminal atrocity against their neighbors.

What does Iran want next?

We just want to live a normal life. We are content with our size, with our population, with our geography, with our natural resources. We want to have serious interaction with the rest of the world and with our region. We do not want to be excluded from the region in which we have been a major force for far, far longer than many countries have existed, both in this region and in your part of the world.

Is there potential for collaboration, coördination, discussion over the flashpoints with the United States?

This is a test for us to see whether the United States is ready to deal with realities, to set aside this language of coercion and force. I’ve been repeating this, and I don’t know why nobody is listening. The United States is a founding member of the United Nations. And I believe when they wrote in Article 2, Paragraph 4 of the Charter that the threat of the use of force is against international law … Now if a country, on a daily basis, says all options are on the table, meaning they are threatening to use force against sovereign states, this is the law of the jungle, not the law of the United Nations.

I think the United States would do itself a lot of good if it abandoned this language. I mean, the actual use of force by the United States has not paid any dividends, neither for U.S. policy nor for the American people. It has only cost you as taxpayers a lot of money. … It is extremely important to start recognizing that the Iranian people have two qualities: they resist pressure but they respond very positively to respect.