With negotiations paused until a new hardline administration takes office in Tehran, the chances of reviving the 2015 Iran nuclear deal anytime soon are not bright. Moreover, even successful talks might not stop Iran’s leaders from pursuing nuclear weapons. The Biden administration needs to find a better way to deter them.

It’s still possible, perhaps even likely, that the desire for sanctions relief will prompt the Iranians to rejoin the deal, formally known as the Joint Comprehensive Plan of Action, once they conclude the U.S. will make no further concessions. That would roll back some of Iran’s recent advances, including its enrichment of uranium to 60% purity and its production of uranium metal, used in nuclear warheads.

Returning to the status quo ante, though, will also highlight the original deal’s fundamental shortcomings — its fast-approaching sunset clauses, most notably. When the JCPOA’s key provisions lapse in 2030, there will be no limits on the size of Iran’s nuclear infrastructure, the number or types of centrifuges it can run, or even the amount of weapons-grade fissile material it may possess or produce. By 2023, just two years from now, there will be no limits on Iran’s ballistic missiles, very effective delivery vehicles for nuclear weapons.

That the Biden administration hopes to reach a “longer and stronger” follow-on agreement reflects its recognition that the JCPOA is not sufficient. The trouble is, incoming Iranian President Ebrahim Raisi has made it clear that Iran has no interest in such a deal. Inducements rarely, if ever, alter Iran’s behavior and are unlikely to change the minds of either Supreme Leader Ayatollah Ali Khamenei or the new president.

Nor is Iran’s insistence that it doesn’t intend to develop nuclear weapons credible. If that were true, the regime could have pursued far less costly alternatives to building its own extensive enrichment capability. Establishing a civil nuclear industry to generate electricity, using fuel furnished from outside the country, was always an option — one that Iran consistently rejected. Evidence of its work on designing nuclear warheads, revealed in the nuclear archive Israel ferreted out of Tehran, only confirms its interest in a weapons program.

If the U.S. cannot persuade Iran to temper such ambitions using carrots, which seems unlikely given Iran’s determined pursuit of a large nuclear infrastructure, it must find more effective sticks. To start, the Biden administration should reframe its stated objective and be clear the U.S. is determined to stop Iran not just from acquiring a nuclear weapon, but from being able to produce a bomb quickly. It’s very likely Iran hopes to become a threshold nuclear weapons state similar to Japan, which does not have a nuclear weapon but has all the means to produce one very quickly. Unlike Japan, Iran is a threat to its neighbors and must not be in a position where it could effectively present the world with a nuclear weapons fait accompli at a time of its choosing.

The Biden administration should thus tighten its declaratory policy to say Iran will not be allowed to become a nuclear weapons threshold state. In theory, negotiations could defer such an outcome. One way to do so would be to extend the JCPOA’s sunset clauses for another 10 to 20 years. A better alternative would be to impose strict limits on Iran’s production capabilities and the numbers and types of centrifuges it can run, in perpetuity.

If Raisi’s government continues to reject follow-on talks, however, the U.S. must make the costs of pursuing a threshold capability far clearer. To do so, the Biden administration should consider providing Israel the GBU-57 Massive Ordnance Penetrator, a 30,000-pound mountain-buster, as some in Congress have advocated. Such a weapon could be used to destroy Fordow, the underground Iranian enrichment facility, as well as other hardened nuclear sites.

Of course, the White House would need to reach a firm understanding with the Israelis about triggers for the bomb’s use. But being prepared to provide Israel with such a fearsome weapon and leasing the B-2 bomber to deliver it would send a powerful message. The Iranians may doubt whether the U.S. would follow through on its threats; they won’t have any trouble believing the Israelis will.

In fact, providing the GBU-57 to Israel may be the best inducement for Iran to negotiate a “longer and stronger” deal. Only then might the regime accept that the U.S. is serious about preventing Iran from acquiring a threshold status — and that Iran risks its entire nuclear infrastructure in the absence of an agreement limiting it. Under such circumstances, Iran’s leaders will have an incentive to get something now for accepting an outcome that the U.S. and Israel might otherwise impose.

Dennis Ross is counselor at the Washington Institute for Near East Policy and served in senior national security positions for Presidents Ronald Reagan, George H.W. Bush, Bill Clinton and Barack Obama. He is co-author of “Be Strong and of Good Courage: How Israel’s Most Important Leaders Shaped Its Destiny.” This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.

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