In 2015, as the United States negotiated the Joint Comprehensive Plan of Action (JCPOA) with Iran—an agreement Israel was not a party to—we argued in Foreign Affairs that Israel and the United States should pursue a parallel agreement to ensure that any U.S.-Iranian deal would be durable and aligned with Israeli interests. Israel and the United States shared the same goal—preventing Iran from acquiring nuclear weapons—but differed over threat perceptions, historical trauma, timing, and tolerance for alternatives to diplomacy, such as sanctions, covert action, and airstrikes. A parallel agreement would help create a unified front and coordinate responses if Iran crossed any redlines.

In the end, however, Israel and the United States never made a pact of their own. The consequences were severe. The JCPOA became a source of friction between the U.S. and Israeli governments and created the sense among people in Israel and Arab Gulf countries that the United States had discounted their security. It was politically vulnerable from the moment it was signed.

The deal temporarily restricted parts of Iran’s nuclear program, but it did not stop Tehran’s ballistic missile buildup or its support for proxies. Key provisions were set to expire after just a few years. And Israel and the United States never jointly prepared for the possibility that Iran would stop complying with it, which Tehran eventually did after the United States unilaterally withdrew from the deal in 2018. Altogether, the lack of Israeli buy-in around the JCPOA created the conditions that put Iran, Israel, and the United States on a collision course a decade later.

In many ways, the current moment resembles the lead-up to the 2015 nuclear deal. Once again, Tehran and Washington are engaged in nuclear talks. And once again, the United States is at risk of offering Iran great relief in exchange for relatively little—much to the chagrin of Israel and certain Gulf countries. The U.S.-Iranian memorandum of understanding reopens the Strait of Hormuz, stabilizes energy markets, suspends the war for another 60 days, and creates a diplomatic channel to keep negotiating. Yet it does not resolve the core disagreements that produced the crisis in the first place: Iran’s nuclear ambitions, missile programs, and support for proxies. The negotiations could thus freeze the battlefield while strengthening Tehran’s hand. The memorandum, after all, grants Iran the time, money, and legitimacy needed to reconstitute while deferring real resolution for another day.

Israel and the United States must therefore do now what they failed to do in 2015: get on the same page. That means they need to forge their own deal about what an acceptable nuclear agreement would look like and coordinate their responses, should negotiations with Iran fail to produce an agreement. Otherwise, the blood, treasure, and prestige both countries have spent fighting Iran and its proxies might all be for naught.

BAD COP, RELUCTANT COP

From the start, Israel and the United States have had different Iran war aims. For Israel, the Iranian threat is existential. The country will not accept an Iran that has nuclear capabilities, a shield of ballistic missiles, and a regional ring of fire controlled by a regime that openly calls for Israel’s destruction. Israel’s war against Iran was meant defensively, to prevent a repeat of the slaughter on October 7, 2023, when Hamas killed 1,200 people in Israel and took 200 more hostage, or even a repeat of the Holocaust in Europe in the early 1940s. In Israel’s view, the only way to guarantee its safety was to replace the Iranian regime with a government that was not hostile to Israel and would give up Iran’s nuclear ambitions as well as its efforts to destabilize the region. After the Iranian regime was........

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