When Hassan Rouhani, the new president of Iran, speaks at the United Nations General Assembly this week, the world will hold its breath.

Well, we should. Although there is understandable skepticism from various quarters, the available evidence strongly suggests that Rouhani is the real deal: a genuine reformer looking to change Iran inside and out. In particular, he clearly wants an end to the multilateral sanctions and is willing to compromise on Iran’s nuclear program to get it.

The rough outlines of a nuclear deal seem to be crystalizing as fast as ice-nine. Iran would halt enrichment of uranium beyond 5 percent purity, accept limits on how much low-enriched uranium it could have in the country, cap the number (but not the quality) of centrifuges it would retain, forswear plutonium separation, and agree to an intrusive inspections regime usually referred to as the “Additional Protocol plus.” In return, the international community would lift most, if not all, of the multilateral trade and financial sanctions imposed on Iran.

Such a deal would be a godsend for the United States, Israel, Saudi Arabia and our other allies in the region and beyond. If we can get such a deal, we should take it.

But the current giddiness should also put us on our guard. We have seen other moments like this with Iran and elsewhere in the Middle East that ultimately proved disappointing. For roughly two decades, experts on the Middle East have believed that the broad contours of an Israeli-Palestinian peace were well known. During the 1990s, it seemed inevitable that just such a deal would be struck and the conflict finally ended. Of course, it never happened. We still think we know what the deal looks like, and most believe it self-evident that Israelis and Palestinians should accept it. But they haven’t, and few expect they will any time soon.

We need to prevent the traps that have hamstrung the long-expected Israeli-Palestinian peace from doing the same to a U.S.-Iranian nuclear deal. Here's how:

Address American Concerns

Among Americans, there are three principal concerns about this deal: that the Iranians will cheat on a deal and surprise the world with a nuclear arsenal, as the North Koreans did; that even if the Iranians don’t cheat, the deal will leave Tehran with a latent nuclear weapons capability that it might someday exploit; and, finally, that Iran’s behavior beyond its nuclear ambitions—its support for terrorism and efforts to destabilize the Middle East—may cause some to oppose a deal that fails to address those issues.

To minimize the risk that Iran would even try to cheat, a nuclear agreement needs to contain two critical features that—as we learned, painfully, with Iraq and North Korea—are key to successfully disarming a state that does not want to be disarmed. First, the deal needs to include provisions for intrusive, comprehensive, surprise inspections and continuous monitoring. As in Iraq, U.N. inspectors need to be able to go anywhere at any time, without delay. That permission was absent from North Korea before 2006, from Iraq before 1991, and from Iran today, allowing all three to build and operate secret facilities for some time. However, the additional protocol of the Non-Proliferation Treaty was designed with just this danger in mind. It empowers a U.N. inspection regime akin to the one in Iraq after the Gulf War ended in 1991. We need to remember that those inspections did eventually work, even if it took at least five years to convince Saddam to shelve his WMD programs.

Moreover, the Iraq experience demonstrated that inspections need to be unhindered and comprehensive, but not perfect. Before 2003, we believed that the inspections could only be a success if they found every jot and tittle of Saddam’s hidden WMD programs, assuming that he would keep making progress with whatever was left. What we learned from our post-invasion studies of Iraq’s WMD programs was that the inspections worked not because they found every trace of those programs, but because they found more than enough to keep the sanctions in place. And because Iraq could not bear the sanctions, Saddam eventually gave up all of his WMD, even those which the inspectors did not find.

Nevertheless, the Iraq and North Korea experiences demonstrate that inspections alone are insufficient. Only if intrusive inspections are tied to the threat of painful sanctions can they work. In North Korea, the threatened sanctions were inadequate—mostly just the withholding of benefits that Pyongyang valued less than a nuclear arsenal. In the case of Iraq, the inspections were backed by draconian sanctions which Saddam ultimately concluded he had to have removed, even if it meant surrendering his WMD. There is an important codicil to the Iraq example that's relevant to a possible Iran deal: Saddam only planned to give up his WMD temporarily and was working assiduously to undermine the sanctions, at which point he planned to start rebuilding his programs. Thus, inspections may only work as long as the threat of sanctions is credible.

With Iran, painful sanctions are already in place. They helped bring Rouhani to power, and convinced Ayatollah Ali Khamenei to at least let him explore a deal with the West. The danger is that if the sanctions are simply lifted, Iran may no longer feel the pressure to abide by its part of the deal, especially because it is typically so hard to get the U.N. Security Council to agree that a country has violated its international obligations and to impose (or re-impose) sanctions. For that reason, it would be preferable to leave the sanctions in place and simply suspend them for renewable periods. That way, any time that Iran is suspected of cheating, it would only require an American, British, or French veto to snap the sanctions back in place. However, as long as Iran held up its end of the deal, the sanctions could be suspended indefinitely—an approach to long-term situations that national governments and international organizations employ all the time.

What may be harder for many Americans and other Westerners to accept is that, as part of any negotiated resolution, Iran is going to have to be allowed to retain the ability to enrich uranium and to have a limited program to do so. That means that Iran will always have some residual capacity to manufacture nuclear weapons. There is no good reason why Tehran should need this capability, but it has become a matter of national pride for the Iranians. Given how much the Iranians have invested in this program, how much progress they have already made, how committed to it they have become, and how much pain they have endured to hang on to it, it is simply not plausible that they will agree to give it up altogether.

This is a limit we should be willing to accept. It may not be ideal, but it should be more than adequate. If Iran’s enrichment capability is capped and constrained by intrusive inspections, and of greater importance still, its ability to work on weaponization is precluded by those same inspections, that residual capacity would be minimal. It would take Iran at least six months and probably more like a year to assemble a crude nuclear device, once it decided to do so, and it would be highly likely that the inspectors would discover such a gambit long before it came close to fruition. Even the Israelis understand this, with former Prime Minister and Defense Minister Ehud Barak indicating that he is ready to accept ongoing Iranian enrichment and even possession of a small stockpile of low-enriched uranium as part of a deal with Iran to cap and inspect its nuclear program.

Finally, we should not assume that even if we can somehow achieve the elusive nuclear deal with Tehran, it will mean the end of all of our problems with the Islamic Republic. Even Rouhani and his stunningly moderate foreign minister, Mohammad Javad Zarif, have warned that Iranian relations with the United States may never be friendly. Tehran will doubtless continue to support insurgents, terrorists, and others determined to subvert American allies. For this reason, the United States needs to distinguish between its own unilateral sanctions and the multilateral sanctions imposed on Iran over the past seven years in response to its defiance on the nuclear issue. The latter should be suspended, whereas the former ought to remain in force as long as Tehran’s other objectionable behavior does not change. However, secondary sanctions that the U.S. imposes on other countries for refusing to comply with our newest unilateral sanctions also need to be withdrawn—both because Tehran will probably insist, and because our failure to do so will bring us into conflict with our trade partners in Europe and East Asia.

Address Iranian Concerns

We won’t be the only skeptics going into this deal. Many Iranians are equally dubious, especially the regime’s hardliners, who continue to see the U.S. as hell bent on overturning the Islamic Republic. To a considerable extent, it is going to be up to Rouhani and the Iranian moderates to address their problems. But we should be prepared to help.

Rouhani may ultimately need more than the removal of the multilateral sanctions. He may need the U.S. to pledge, as we did to Cuba after the 1962 Missile Crisis, that we will not invade or otherwise try to overthrow the Iranian regime. He may need a commitment from the international community to help Iran develop its nuclear energy sector, which can be done by providing lightwater reactors that would not significantly bolster Iran’s ability to build nuclear weapons. He may also need economic support from international financial institutions like the World Bank and the IMF. He might even want to try to bring Iran into the World Trade Organization, although that seems unlikely given Khamenei’s insistence that the WTO is a subversive organization whose requirements would undermine the Islamic regime. The United States and our allies ought to be ready and willing to agree to any or all.

Moreover, we also ought to hold out the prospect that if Iran is willing to make deeper concessions, so should we. For instance, if the Iranians were willing to give up their support for terrorism, end their opposition to an Arab-Israeli peace, and otherwise cease trying to harm American allies, the U.S. should be willing to extend positive economic benefits such as trade credits, investment guarantees, and even aid programs. We could also offer to accept Iran as a political player in the region, including Tehran in events like the Geneva talks on Syria. Finally, if Iran were willing to curb its own arms purchases, deployments, and military operations, we ought to be open to establishing a regional security forum that could forge confidence building measures and perhaps someday arms control agreements that would help Iran address its legitimate security concerns and allay the fears of its neighbors as well.

All of this seems far away. Doubtless it is. But Rouhani has taken a bold step forward and appears to want to take more. We should not ignore our concerns, just as he cannot ignore those of his domestic rivals. But we must be ready to address all of them, take some risks on our side, and help him to convince others in Tehran to do the same. This may well be our best chance to solve one of the greatest problems facing the Middle East and American foreign policy. We may not have another. And if we cannot grasp this one, we will be left with a choice between the two worst options of all: living with a nuclear Iran, or embarking on another war in the Middle East to prevent it.

Obama's Iran Nuclear Deal Could Be a Major Triumph

By John B. Judis

How to Fix the Iran Nuclear Deal

By Dennis Ross

Here's the Deal the U.S. and Iran Should Make Right Now

By Kenneth M. Pollack

An Israeli Strike on Iran Just Got More Likely

By Ben Birnbaum

Page 1