Michael Singh is managing director of the Washington Institute for Near East Policy.

With the first round of nuclear talks with Iran’s new, and newly pragmatic, negotiating team in the books, the Washington policy debate about Iran has shifted from whether a deal is possible to what sort of deal is acceptable. While such discussions can often seem a miasma of centrifuge counts and enrichment levels, there are, in fact, two distinct paths to a nuclear deal with Iran.

The first path is one in which Tehran would receive relief from sanctions in exchange for putting strict limits on its nuclear activities, such as restricting uranium enrichment to low levels. The success of such an agreement would depend on ensuring that Iran could not use declared nuclear activities as a cover for covert activities aimed at developing a nuclear weapon. It would also depend on ensuring that the deal was not easily reversible, so Tehran could not renege once pressure had been alleviated.

There are ways that sanctions relief could be made more easily reversible — for example, channeling oil payments to Tehran through a single mechanism that could be blocked in the event of noncompliance — but none of these is fail-safe. The efficacy and durability of a deal over limited enrichment would rest on Iranian transparency. To be meaningful, transparency measures would have to include allowing inspectors unfettered access to sites of their choosing, not just those declared by Iranian officials, and a comprehensive accounting of Iran’s past and present nuclear work, including the military elements of its nuclear program, such as weaponization research.

Coming clean in this manner is a prerequisite for the success of any deal that leaves in place dual-use nuclear capabilities. Countries that have divulged their nuclear secrets, such as South Africa, have proceeded to cooperate peacefully with the international community on atomic energy. Those that continued to obfuscate despite agreements, such as North Korea, experienced deeper isolation and external tensions.

Iran appears to prefer the latter model. While its officials profess a desire for cooperation, they continue to dismiss as “unfounded allegations” evidence deemed “credible” by the International Atomic Energy Agency that Iran has engaged in nuclear work related to weapons. Iran continues to deny inspectors access to suspected nuclear sites and key personnel, and it seeks to constrict their activities within the bounds of its declared nuclear program.

Even in the best circumstances, it would take time to establish confidence that Iran had truly given up its nuclear weapons aspirations. Allies such as Israel and the Gulf states would distrust Iranian intentions, while Iranians would bristle at the intrusiveness of inspections. Absent a strategic shift by Iran, a deal on limited enrichment is more likely to increase those tensions than to defuse them: Iran would seek to hide or deny activities for which the United States and its allies have convincing evidence; Iran’s adversaries would seek to match its nuclear capabilities; and erstwhile allies such as Russia and China would drift away from the unlikely coalition currently led by Washington.

The unlikelihood of a change of heart by Iranian leaders suggests a second, more straightforward path to an agreement: requiring Iran to dismantle its nuclear program in exchange for any relief from sanctions, which would be increased should Tehran refuse to yield. In this model, Iran would have to suspend enrichment- and reprocessing-related activities as demanded by the U.N. Security Council, dismantle its underground enrichment facility at Fordow and export its stockpiles of enriched uranium, among other steps.

The obvious objection to such a deal is that it may be too difficult to achieve; even U.S. negotiators have characterized this stance as “maximalist.” But any deal must be evaluated in comparison to plausible alternatives, not in isolation, and Iran’s alternatives are bleak. Iran’s economy is under severe strain because of the sanctions. If Iran tried to “break out” for a nuclear weapon, the United States and Israel have made clear that they would strike a devastating military blow.

And contrary to conventional wisdom, time is not on Iran’s side. With each passing day, Iran’s economic predicament deepens and its nuclear program expands. But while the former threatens Iran’s well-being, the latter does not improve it. Adding to its centrifuge inventory and uranium stockpile merely edges Iran closer to Western “red lines” while making it no less vulnerable to attack.

The United States possesses powerful leverage in the nuclear talks: Its negotiating position is eminently reasonable. The West is offering Iran something it desperately needs — sanctions relief — in exchange for something it has little ostensible use for — enrichment and reprocessing — given its disavowal of nuclear weapons. That’s hardly a maximalist position.

It is commendable that the United States and its allies hope earnestly that Iran would take the path of true transparency and cooperation; indeed, President Hassan Rouhani’s “ charm offensive ” is so beguiling because it appeals to those hopes. But we, and perhaps even Rouhani, cannot compel Iran to make such a fundamental change in course. We can, however, with firmness at the negotiating table and confidence in our leverage make plain the alternatives and force Tehran to confront, rather than evade, the consequences of its choices.