Secretary of State John F. Kerry arrives in Geneva (Jason Reed/AFP pool photo)

The possibility of a nuclear deal with Iran appeared closer than ever on Friday, as Secretary of State John Kerry flew to Geneva to take part in negotiations between Iranian and Western diplomats. While there's still no formal deal, an agreement would likely require Iran to temporarily freeze some nuclear activities in exchange for relief from economic sanctions.

To understand what's happening in Geneva this week, and how it fits into the larger arc of U.S.-Iran relations, I spoke with Kenneth Pollack of the Brookings Institution, who helped engineer the Clinton administration's 1990s effort to reach a similar deal. Pollack has written frequently on Iran, including in his most recent book, "Unthinkable: Iran, the Bomb, and American Strategy." A lightly edited transcript of our phone conversation follows. An abbreviated version appears in print Saturday.

How big of a deal is what's happening in Geneva right now?

The first answer is of course that we don't know -- because we don't know what the deal looks like, and at this moment in time we've got to recognize that, be aware of it. Until we see the text of the agreement it's hard to really assess how important this is.

That said, at some level you can say that any agreement between the United States and Iran, between the P5+1 [the five permanent members of the United Nations Security Council plus Germany, which lead negotiations with Iran] and Iran on its nuclear program, would be very important. It will be the first real deal ever. We've had partial deals, we've had tacit agreements between the Iranians and the Europeans, we've had other things, but we've never had a full-on deal like this. And I think that this ought to give us confidence that the Iranians are serious, that [Iranian President Hassan] Rouhani is serious when he says that he is looking to strike a deal on the larger nuclear issue and that he has got at least some degree of support from [Supreme Leader Ayatollah Ali] Khamenei to do so.

We do have to be careful about that. I don't think that Ayatollah Khamenei has necessarily given his carte blanche, his a priori blessing, to any deal that Rouhani strikes. But clearly Rouhani is in a better position to negotiate what would be an acceptable deal, to us, than any of his predecessors. Getting this kind of interim deal with the Iranians would be another very important step in reassuring us that that's the case.

If we take a long view, the longest view necessary, how did we get to this point?

You can go back as far as you like, but I think I will go back to the sanctions themselves. It is clear that the sanctions have hurt the Iranians very badly, and I think that was registered in Iran's presidential election, over the summer, which Rouhani won, in a surprise, I think, to everyone, particularly to Rouhani himself and probably to Khamenei. He was clearly elected because Iranians want change, and clearly one of the most important changes they want is they want an end to the sanctions and an end to Iran's isolation. Rouhani has clearly taken that, seemingly with a lot of public support, and said, "The way that we're going to get an end to sanctions and an end to Iran's isolation is by being willing to make a very significant compromise on our nuclear program."

I think the importance of the sanctions is really reflected in the fact that that was Rouhani's opening political gambit [on taking office in August]. If you had interviewed me right after the Iranian election and asked, "What do you think Rouhani's going to do next?," I think my best guess at that time would have been that Rouhani would start small, start with some economic and political issues within Iran as a way of building up some important political wins, getting some political capital, and then maybe later on he would turn to this incredibly difficult, incredibly thorny issue of the sanctions and the nuclear program and the relationship with the United States.

That's not what happened at all. Instead, Rouhani, right out of the gate, said, "I want to tackle this big thorny set of issues, because I want to get the sanctions lifted, because that's the most important thing I can do right now for the Iranian people." And I think that speaks to the fact that the sanctions really were painful, that they were a critical element of his election, and they were a critical element of his plans for Iran moving forward.

Given the importance of sanctions in bringing Iran to the table, it would seem to matter greatly now how the United States and Europe deal with reducing sanctions or not reducing them, the rate at which they do it and in response to what triggers. How will that process work?

You've put your finger on what I fear will be the most difficult question of all. I think it some ways it's easy to lay out what the Iranians would be expected to do. Yeah, there are some discrepancies about the exact number of centrifuges, that kind of thing, but these are minor details. We and the Iranians and our allies all have a pretty clear sense of what we would be asking from the Iranians. The really hard part is what they can expect in return from us.

There are a few different sets of issues here. One set is of course that, in addition to the U.N. sanctions against Iran, there are also very important American unilateral sanctions, which include secondary sanctions against any foreign company or country that is engaged in trade with Iran. And those sanctions, in almost every case, are predicated not just on Iran's nuclear activities, but also on their support for international terrorism, their opposition to the Middle East peace process and a whole list of other things.

So, if the Iranians insist the U.S. repeal its unilateral sanctions, I think it's going to be very hard for the president to go to Congress and say, "Will you do this?" Because I think Congress will rightly turn around and say, "Those sanctions are to get the Iranians to turn their behavior around, not just on the nuclear issue, but on all these other things. Until they're willing to deal with those other things, we're not going to repeal those sanctions." So that's one very important potential sticking point.

Another is that the way that, historically, these arms control and disarmament agreements have worked is that there is a very intrusive inspection regime backed up by painful sanctions. What we've seen is that it's very difficult to get the U.N. Security Council to impose sanctions. It's even hard to get it to re-impose sanctions and to punish states for recalcitrance. So I think there's a real fear on a lot of people's parts that if we were to simply lift the sanctions as part of a deal with the Iranians, then it would be very hard to reimpose those sanctions, and therefore the Iranians might rightly conclude that they could cheat. And even if this Iranian government doesn't [cheat], a future Iranian government might. They might say, "It's been five years, 10 years since the agreement was struck. Everyone's forgotten about the deal on our nuclear program. We can go ahead and do this stuff, and it's pretty unlikely that anyone will be able to muster the support at the Security Council to pass new resolution."

So a better way to handle things would actually be to suspend the sanctions. Pass a new resolution that simply says that for the next six months, the sanctions aren't in effect, and this can be renewed indefinitely into the future. The U.N. does this lots. From our perspective, from a strategic perspective, this is a better way to handle things. For the Iranians, it may be unacceptable. They may basically say, "You expect us to give up our nuclear program, in return for only the suspension of sanctions, which anybody with a Security Council veto could immediately overturn on a whim? That isn't fair to us." So that would be a second big hurdle out there, and there are a whole bunch of others.

We've never gotten to this point before, but there were previous outreaches under the administration of President Mohammed Khatami, from 1997 to 2005. What's different now, in both the United States and Iran, and what's not different?

The most important difference, honestly, is on the Iranian side. As you know, I was part of the Clinton administration at the time [of a mid-1990s outreach effort], I was the Iran guy at the White House at the time, and we wanted that rapprochement. We were actually starting to move the wheels of government to make that rapprochement happen on the American side. President Clinton himself was personally very vested in it. If the Iranians could've come through, we would've come through.

The problem was on the Iranian side, and I think that's really the difference this time around. On the Iranian side, it was really just President Khatami who wanted it, and he made it pretty clear that he didn't have Khamenei on board with him and that he faced a huge amount of opposition from hard-liners [within Iran]. In fact, all of our behind-the-scenes conversations with Khatami's people were about things that we could do that would help him win these arguments with Khamenei and with the hard-liners.

What's different this time around is that Rouhani clearly has the blessing of the supreme leader to conduct the negotiations.

Do we have any idea how that happened? How he got Khamenei on board?

We don't. This will be a great story that hopefully we'll learn in the future. We know that Rouhani's close to Khamenei. Rouhani was a close aide of his in a whole variety of different capacities over the past 20 years. I think that Khamenei is a lot more comfortable with Rouhani than he ever was with Khatami, who was a much more peripheral figure, not well known to the ayatollah in nearly the way that Rouhani is. I suspect that Rouhani had a conversation with Khamenei about the kind of deal that he believed he could get the Americans and Europeans and everybody to agree to. I think he probably persuaded the ayatollah that it would be good for Iran, that it would be acceptable, that he could get sanctions lifted.

And either they had a conversation about this or Khamenei recognized it on his own, that his people were deeply desirous of change. And what happened in 2009 [with mass protests over President Mahmoud Ahmadinejad's disputed reelection] fed into that. In the presidential election of 2013, the Iranian people registered in an overwhelming fashion that they wanted change. That election result was likely also part of bringing Khamenei around to at least allowing Rouhani to explore what kind of deal he could get from the Americans.

The Israelis and Saudis obviously oppose a deal. What role are they playing in the process now, and how concerned should the Americans be about that?

Another very important question. I think that there's a good side and a bad side to Israeli and Saudi opposition. The good side is that the Israelis and Saudis are in effect playing "bad cop." Whether the Israelis are intentionally playing this role or they just flat-out oppose a deal, I think we don't know. The Saudis, I think they genuinely oppose a deal.

With the Israelis, it's very mixed. What we don't know is where [Prime Minister Benjamin] Netanyahu is on this. We don't know if he just wants to play "bad cop" or if he bound and determined to oppose any kind of a deal, in the way that the Saudis are. The good side of that is that it's going to hold everybody's feet to the fire and hopefully will allow us to get the best deal possible from the Iranians.

The bad side is that if we actually can get a deal from the Iranians, it will inevitably be a "partial deal," in Netanyahu's terminology. And a partial deal is the only kind of deal we are going to get from the Iranians, because they've made it clear over and over again that the terms that Netanyahu has laid out are unacceptable to them. So then the question becomes, will the Israelis and the Saudis try to block it? That could be very, very bad -- not just for the United States, but for both the Saudis and the Israelis.

I think that's why the Saudis did not want to take the seat that had been allocated to them on the Security Council, because they don't want to be seen as publicly opposing a deal with Iran, and they don't want to be the only country on the Security Council to vote against such a deal.

Because they're worried it could turn international opinion toward Iran?

Exactly. And if they tried to somehow scuttle a deal, a deal that the U.S. and foreign governments all believed was a good deal, then that could be very damaging to U.S.-Saudi relations. People would see it as the Saudis trying to drag us into a war with Iran that was unnecessary.

It's the same thing on the Israeli side. If the Israelis actually try to kill a good deal with Iran, even if it is a partial deal, it could have a ruinous impact on the U.S.-Israeli relationship. A lot of Americans would see it as the Israelis trying to drag us into a war with Iran. I can't imagine anything worse for the U.S.-Israeli relationship.

Let's say the process falls apart or drags along under opposition from Israel, or the Saudis, or from within the U.S. Congress. At some point does Europe get fed up with this and start easing Iran sanctions on their own?

Yes. This is the other danger of the Iranians putting a good deal on the table, one that everybody else in the international community looks at as a good deal that will address everybody's concerns and will make it highly unlikely that Iran will cheat, and the United States decides not take it, either on our own or because one of our allies somehow convinces us. I think you would see international support for the containment of Iran erode very quickly.

That is, in effect, what happened with Iraq after 1995 and 1996. Remember that, in the case of Iraq, no one really thought that [Iraqi leader Saddam Hussein] was complying. That's what's kind of amazing. In this case, Iran would likely be seen as the compliant party, the one that was trying to work out a deal, and it would be the United States that was being recalcitrant. It would be very difficult to hold in place the sanctions and the other measures to isolate and pressure the Iranians.

Some of the toughest hurdles to any deal would be within Washington and within Tehran. We know the U.S. politics of this. But, in Tehran, how much influence does Supreme Leader Khamenei actually have, or is actually willing to deploy, within the system if this becomes a big fight?

This is another great question, it's one that we need to focus on. I'm very hopeful about this, and even guardedly optimistic at this point in time, that we're actually going to get a deal. And I absolutely believe that this may well be the best opportunity that we have ever had, and maybe that we will ever have, to get a deal with the Iranians, get it off the table and maybe even start a larger process of thawing the relations.

That said, as you point out, it's the domestic politics on both sides that are ultimately going to decide this. In the case of the Iranians, what we've seen is that Khamenei does have, as best as any outsider can tell, all of the power he needs to force this through the system, to overcome the opposition of the hardliners.

But. We've never seen Khamenei actually overrule the hard-liners on an issue of this kind of importance. We've seen [previous supreme leader Ruhollah] Khomeini do it, famously, at the end of the Iran-Iraq War. The hard-liners wanted to keep fighting, and [later-president Hashemi] Rafsanjani and the pragmatists wanted to end it. In the end, although he said it was more bitter to him than "drinking poison," Khomeini agreed to overrule the hard-liners. We haven't seen that with Khamenei.

Well, Khomeini was a much more confident leader.

Right, exactly. Khomeini was much more confident; Khamenei lacks that confidence. He clearly has given Rouhani the freedom to maneuver, he's given him the freedom to do this, that's got everyone hopeful. At some level, Khamenei has got to have thought through that he might have to confront his hard-liners, to get them to agree or over-rule them. But we can't be certain. We just don't know where Khamenei is now, what he's thinking about. Or maybe he's thinking right now that he'd be glad to overrule the hard-liners, but maybe when it comes down to it he'll lack the courage of his convictions.