For all the attention devoted to the terms of a possible agreement between the United States and Iran, the more fundamental obstacle may be whether Tehran believes Washington will honor one.
The history of US-Iran diplomacy has left Iranian leaders deeply skeptical that American commitments will endure, whether across administrations or even through the course of a single presidency. President Donald Trump withdrew from the 2015 nuclear agreement in 2018 despite Iran’s compliance at the time, restored sweeping sanctions, and subsequently turned to military force. More recently, the Memorandum of Understanding (MOU) that halted an earlier phase of the current war offered another test of whether an agreement on paper could become a durable political settlement. From Tehran’s perspective, that test failed.
This credibility problem helps explain an otherwise puzzling feature of Iran’s strategy. Tehran continues to express interest in negotiations and a definitive end to the war while refusing to relinquish its most consequential source of leverage: its ability to restrict transit through the Strait of Hormuz. Iranian officials increasingly regard control over Hormuz as fundamentally different from promises of sanctions relief. One ultimately depends on decisions made in Washington. The other is leverage Tehran controls itself.
The previous memorandum was supposed to provide the foundation for a broader settlement, including economic relief for Iran, an end to the war in Lebanon as part of a regional cessation of hostilities, and Iranian arrangements for maritime transit through Hormuz. But implementation quickly became contested. Iranian officials concluded that Washington wanted the agreement’s most important benefit for itself, restored shipping through the strait, without accepting the transit arrangements Tehran the MOU left for Iran to determine or fully deliver the economic and political concessions it had been promised.
American sanctions against Iran cannot simply be switched off
That experience reinforced a problem much older than the current war. American sanctions on Iran are not a switch a president can simply turn off. They are a dense architecture constructed over decades through congressional statutes, executive orders, Treasury regulations, and thousands of individual designations. They include primary sanctions largely barring US persons from commerce with Iran and secondary sanctions that threaten foreign banks and companies for specified dealings with the country. Those secondary measures leverage access to the American market and financial system to give ostensibly unilateral US sanctions global reach.
Much of this architecture is embedded in law. Congress has enacted sanctions targeting Iran’s energy exports, financial sector, Central Bank, shipping, arms trade, the Islamic Revolutionary Guard Corps, and other parts of its economy and state. Some statutes impose conditions a president must meet to waive or terminate sanctions. Iranian entities can also be designated under multiple authorities, meaning removing one restriction may leave others intact.
A president still has substantial power to provide relief, but the form matters. Some sanctions can be removed through executive action, while congressionally mandated measures may instead be waived, sometimes for renewable periods, without eliminating the underlying law. Licenses can authorize transactions that would otherwise be prohibited, while changes in enforcement can create additional room for economic activity. But these forms of relief remain vulnerable to reversal: waivers can expire, licenses can be withdrawn, and sanctions or designations can be reimposed.
Sanctions relief may not last or provide immediate economic relief
This creates a problem even before sanctions formally return. Foreign banks and companies deciding whether to reenter Iran must consider whether US relief will last. Secondary sanctions are particularly powerful because access to the much larger US market and financial system gives firms strong incentives to avoid Iran when they fear future penalties. After Trump withdrew from the nuclear agreement, European companies abandoned Iranian business to protect their US exposure. Washington can therefore lift restrictions on paper without necessarily convincing companies that investing in Iran is safe.
The Joint Comprehensive Plan of Action (JCPOA) demonstrated both the possibilities and limitations of this system. The US provided relief from many nuclear-related sanctions, while sanctions imposed under terrorism, human rights, and missile authorities remained. Trump then restored the sanctions eased under the agreement and added others through his maximum-pressure campaign.
Congress underscores why Tehran sees the problem as larger than Trump. Even while the JCPOA remained in force, lawmakers overwhelmingly extended the Iran Sanctions Act through 2026, with significant Democratic support. The then President Barack Obama allowed it to become law without his signature. The extension did not itself violate the JCPOA, but it preserved a major component of the statutory architecture underlying US economic pressure. Now 86 senators from both parties have voted to advance legislation that would extend the law through 2031.
The Strait of Hormuz presents Tehran with ongoing diplomatic leverage
Hormuz presents Tehran with the inverse of this problem. Control over the strait is not a presidential waiver or Treasury license. It is leverage Iran possesses independently, whose economic consequences extend to regional governments and the global economy. Washington cannot unilaterally revoke it.
Iran’s negotiations with Oman illustrate the distinction. Tehran has been discussing a new arrangement with Muscat governing maritime transit. But Mohsen Rezaei, the new secretary of Iran’s Supreme National Security Council, has said that an agreement with Oman over a transit route would be separate from reopening the strait. He has tied that step to broader US concessions, including ending the war and releasing Iranian funds.
An Oman agreement could therefore determine how Hormuz operates after a settlement without itself producing one. Tehran appears intent on retaining its ability to restrict transit until Washington delivers the broader concessions it seeks.
That does not mean Iran has abandoned diplomacy. President Masoud Pezeshkian has called the present moment the “best time” for an agreement. Rezaei has taken a harder line but has likewise framed demands around the conditions for ending the conflict rather than rejecting negotiations altogether. The emerging Iranian position is that diplomacy without enforceable implementation leaves Iran vulnerable, while Hormuz gives Tehran leverage to compel implementation.
Tangible and enduring sanctions relief remain key for Tehran
This makes sequencing central to any agreement. If Washington wants Iran to reopen Hormuz, it may have to make the economic benefits of settlement tangible upfront, including by releasing frozen Iranian assets and providing meaningful sanctions relief. Tehran will also care about how that relief is delivered: whether sanctions are terminated, waived, licensed around, or simply left unenforced.
There is an important asymmetry. Once Iran normalizes transit through Hormuz, recreating that leverage could require another major conflict, while American economic concessions can often be reversed through executive action, expiring waivers, renewed designations, or legislation. This helps explain Tehran’s insistence on a new governance model for the strait: rather than surrender its wartime leverage altogether, Iran wants to institutionalize a lasting role over transit, preserving a means of imposing costs should Washington later restore economic pressure or abandon its commitments.
A durable settlement therefore requires more than mutually acceptable terms. It requires sequencing that gives Tehran reason to believe US commitments will be implemented before Iran relinquishes its strongest leverage. Washington need not accept Iran’s use of Hormuz as an instrument of coercion to recognize the logic driving it. Unless the credibility problem is addressed, another agreement may prove only another pause before the same conflict returns.
Sina Toossi is a Senior Non-Resident Fellow at the Center for International Policy. For more than a decade, he has worked across think tanks, universities, and policy and advocacy organizations, producing research and analysis on US-Iran relations, US Middle East policy, nuclear non proliferation, and human rights abuses in Iran. His analysis has appeared in Foreign Affairs, Foreign Policy, The Guardian, USA Today, and other leading publications, and he is regularly featured in international media. He was selected as a Ploughshares Fund and Horizon 2045 Nuclear Futures Fellow in 2024 and received the Middle East Policy Council’s 2024 40 Under 40 Award.
