By Cliff Kupchan
When Iran’s president-elect Hassan Rouhani takes office on Aug. 3, he will probably bring moderation to at least some aspects of Iranian nuclear policy. It would be tragic if Rouhani’s ascent becomes yet another missed opportunity in the U.S.-Iran saga.

Rouhani was elected with a popular mandate to pursue centrist policies and ease the nuclear standoff. He has consistently called for more transparency in Iranian policy in order to show that Iran seeks nuclear energy and not an atomic bomb. He has called for a more prudent negotiating strategy. He has committed himself to improving Iran’s economy, and he recognizes that lifting the yoke of sanctions is important to achieving that goal.

But Supreme Leader Ali Khamenei will continue to call the shots on nuclear policy, and the common wisdom is that Khamenei is implacably opposed to an agreement. Indeed, Khamenei views the United States with great enmity, and his core constituency — the Revolutionary Guard — will be wary of a deal.

But there are reasons for hope. Khamenei must be aware of Iran’s dire economic plight, which is in significant part the result of sanctions; the inflation rate is over 40 percent; nearly a quarter of men under the age of 25 are unemployed; and swaths of the economy are failing.

Khamenei is aware of Rouhani’s mandate for change, and the election campaign made clear that other powerful groups share Rouhani’s views. Khamenei also very likely knows how the new Middle East handles autocrats who completely ignore popular will.

Soon after Rouhani’s inauguration, the United States must test whether Iran’s new political alignment will produce just happy talk or real policy change.

The best test would be a more creative and forthcoming proposal on an interim nuclear deal — one that would be difficult for Iran to refuse. The essence of the approach should be “more for more” — more sanctions relief for more Iranian concessions on the most threatening aspects of their nuclear program. The sides would agree that after the interim deal is reached, they would negotiate the end-state of Iran’s program within a year.

An interim deal would need to place constraints on Iran’s nuclear program so that the West would be confident that Iran could not quickly acquire a nuclear weapon. The West should add the new demand that Iran suspend installation of centrifuges; the growing size and sophistication of Iran’s program makes a fast breakout more feasible.

The United States should insist that Iran agree to a more frequent and intrusive inspection regime, and continue to demand that Iran cease production of 20 percent enriched uranium, which is dangerously close to weapons grade, and eliminate its stockpile of the material.

That’s a big ask, and in return, the Obama administration has to sweeten the pot.

Iranian elites, including Rouhani, view the disposition of 20-percent enriched uranium as Iran’s key bargaining chip; the West won’t defang this or other key threats without offering significant sanctions relief.

The United States should propose to ease oil and financial sanctions, using presidential waiver authority to the extent permitted by law. The administration should be willing to allow at least several hundred thousand barrels per day of Iranian crude (of roughly 1.2 million barrels per day that sanctions have blocked) to return to the market. The sanctions relief would be implemented in a slow, reversible manner to deter Iranian backsliding. The elements of this deal should be implemented in stages, to build confidence, but could be agreed as a package.

The Obama administration should not seek an end-state agreement at the outset. While general principles on the endgame should be discussed, the issues involved are far too complex — and trust between the sides insufficient — to negotiate a final deal quickly.

Neither should the United States offer any form of a “take it or leave it” proposal. Iran’s elites would almost surely say no to an ultimatum. And that could well lead to military conflict.

The United States has time, but it is limited. Within the next one to two years, Iran will probably acquire the ability to make a bomb faster than the United States could detect and attack the breakout. After that point, diplomacy would be useless.

The West has effectively used sanctions to rattle Iran. But sanctions will not have succeeded until Iran’s nuclear program is tamed. Now is the time to make every effort to reach a deal.