Will the Strait of Hormuz blockade lead to a diplomatic breakthrough, or more violence?

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The United States’ blockade of the Strait of Hormuz, which took effect on 13 April, signals a new Washington strategy to intensify pressure on Iran while diplomacy continues, as the US and Iran engage indirectly to extend the ceasefire beyond its initial two week period. The blockade marks Washington's shift from direct military coercion to disrupting Iran’s maritime trade. The US Central Command is enforcing the blockade across the Persian Gulf on shipping entering or leaving Iranian ports and its coastal areas. Iran, in turn, has threatened to disrupt trade through the Gulf, the Gulf of Oman, and the Red Sea if the blockade continues.¹ While escalation cannot be ruled out, neither the US nor Iran appears to want a new round of kinetic warfare. Instead, Iran’s asymmetrical capability in the Gulf, the risk of prolonged disruption to energy shipping, and international pressure is pushing both sides toward diplomacy.

The ceasefire has mostly held since it began on 8 April. ACLED data show only a few likely Israeli incidents inside Iran on 9 and 10 April, and no further violence has been recorded since the blockade took effect on 13 April as both sides seek a diplomatic breakthrough (see graph below). Tehran has proposed safe passage for shipping through the Omani side of Hormuz, as talks are expected to resume in Pakistan.²

For all the focus on the Persian Gulf and the Sea of Oman, the area saw relatively limited direct military action between the start of the war and the ceasefire agreement, reflecting both sides’ hesitation to provoke a major escalation. The US specifically avoided major attacks on Iranian ports and energy infrastructure in the Persian Gulf to avoid wider retaliation. ACLED records at least 116 incidents in the Persian Gulf and the Gulf of Oman involving all sides, less than 3% of total attacks since the crisis began on 28 February. Of those, US attacks mainly targeted Iranian naval assets, military-linked port facilities, and other non-energy targets (see map below). Iran, in turn, carried out around 46 retaliatory strikes on Gulf ports and oil tankers and cargo ships using drones, sea mines, and missiles. 

Even at this limited scale, Iran’s attacks were enough to disrupt shipping and close the Strait of Hormuz. Although US President Donald Trump threatened to use military force to reopen the strait, including a ground invasion and attacks on Kharg Island, such a move would not likely have shifted Tehran’s position. The risks of a prolonged war and continued shocks to global energy markets would also have been even greater in the case of a ground intervention.

A sustained blockade of the Strait of Hormuz would place both economic and political pressure on Tehran and Washington, but the US would bear the greater cost. For Iran, it would disrupt about 80% of its oil exports and restrict trade in other goods the regime needs to recover post-war costs.³ Even so, it would not necessarily force Tehran to retreat quickly, since the regime may be willing to absorb the pain given the regime’s higher political and security stakes. For Washington, the main effects would be higher oil prices and inflation, which would increase the domestic political cost for the Trump administration as the midterm elections approach. Maintaining the blockade would also require Washington to commit significant maritime assets and capabilities for an open-ended period and without guarantees of an outcome, as the Iranian regime has shown resilience. 

The broader international implications of a sustained blockade would also carry significant costs for Washington particularly at a time when its relations with its allies and others are already under significant strain. China, which has leverage over Iran by buying about 90% of Iran’s oil exports, has explicitly warned against disrupting the strait.⁴ Before the US blockade took effect, China was able to pass its oil tankers through coordination with Iran despite the closure of the strait. The US is taking a risk since any Chinese move to challenge the blockade could force Washington to back down. Meanwhile, France and the United Kingdom are aiming to coordinate a mission to restore freedom of navigation without US participation.⁵

Iran sees the Strait of Hormuz as its main leverage at the negotiation table. It will likely seek better terms on issues such as uranium enrichment, sanctions relief, ballistic missiles, and its regional influence. In the short term, neither Iran nor Washington is likely to want a return to a wider war, especially while diplomacy is still underway. US concessions could push Iran to soften its position over the Strait of Hormuz and the negotiation framework. 

Visuals produced by Ana Marco.