To start, both sides need to reset their expectations, and begin a step-by-step de-escalation that could create the basis for a longer-term resolution. The United States won’t get Iran to the table without some economic relief — either directly or through the European Union, as President Emmanuel Macron of France has suggested. The United States will also need to abandon as a precondition for progress the 12 demands that Secretary of State Mike Pompeo laid out publicly last year. This hard-bitten and resourceful Iranian regime is not going to issue that kind of declaration of surrender.

The Iranians will have to get more realistic, too. It is simply impractical to think that the United States will provide significant sanctions relief without assurances that Iran will immediately begin negotiations on a follow-on agreement that at least extends the timelines of the deal and addresses issues of verification and intercontinental ballistic missiles.

Foreign Minister Mohammad Javad Zarif recently signaled some openness to negotiation of additional terms. While we should have no illusions about how difficult that would be, we should certainly test the proposition. The Iranians have known since the secret talks that we saw this as an iterative process, like other arms control processes, in which one agreement became a foundation stone for further negotiations. The nuclear deal agreed to in 2015 was meant to be the beginning, not the end, of diplomacy with Iran.

Both sides should also seek to reduce tensions more broadly. It is long past time to secure the release of Americans detained, deeply unfairly, in Iran. It is time to stop threats to vital shipping lanes, and stop making Iraq a battleground for American-Iranian competition. We should make an opportunity of the crisis in the gulf and push hard to end the war in Yemen. That conflict is not only a humanitarian tragedy of epic proportion but also a strategic calamity for our gulf partners and a stain on American foreign policy. Afghanistan is another issue to discuss directly, given Iran’s stake in stability there, and Tehran’s ability to disrupt it.

If you asked us to propose a path for diplomacy with Iran, we’d suggest not starting from where we are today.

But we are where we are, and we know where we’re headed, especially given the surplus of mutual enablers in both Tehran and Washington. We have our last, best chance for diplomacy before us. We should seize it.

William J. Burns, a former deputy secretary of state, is president of the Carnegie Endowment for International Peace, and the author of “The Back Channel: A Memoir of American Diplomacy and the Case for Its Renewal.” Jake Sullivan, a senior fellow at the Carnegie Endowment for International Peace, was the national security adviser to Vice President Joe Biden and the director of policy planning at the State Department.

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