US Says It Will Maintain Iran Blockade Despite Strait of Hormuz 'Open' Declaration

On April 17, Iranian Foreign Minister Abbas Araghchi announced that the Strait of Hormuz was "completely open" for all commercial vessels [1]. Hours later, President Donald Trump posted on Truth Social that while the strait was indeed open, the US naval blockade on Iranian shipping would remain "until negotiations with Iran have concluded" [2]. Ship-tracking data told a different story from either government's claims: only five cargo ships and one tanker had crossed into the Gulf of Oman, and no oil tankers had exited the Persian Gulf [1].

This is the state of the world's most important oil chokepoint on Day 46 of the broader US-Iran conflict — a war that began with US and Israeli airstrikes on February 28 and the assassination of Supreme Leader Ali Khamenei, escalated through Iran's mining and closure of the strait, and has now settled into an uneasy standoff where both sides claim the waterway is open while neither acts like it [3].

What the Blockade Actually Is — and Isn't

The US operation, launched on April 13 after the collapse of peace talks in Islamabad, involves more than 10,000 sailors, marines, and airmen, over a dozen warships, and dozens of aircraft [4]. According to US Central Command, the blockade targets only vessels entering and leaving Iranian ports, while freedom of navigation is maintained for other shipping [4]. The Pentagon says the operation has disrupted roughly 90% of Iran's maritime trade [5].

But the word "blockade" carries specific weight under international law. A formal blockade is legally an act of war. The Trump administration has avoided that term in official legal filings, instead framing the operation variously as sanctions enforcement, mine clearance, and freedom-of-navigation operations [6]. The distinction matters: it determines whether allied navies can legally participate, how neutral states must respond, and whether the US is technically at war with Iran beyond the airstrikes already conducted [6].

President Trump initially said all traffic through the strait would be blocked, though military officials quickly narrowed the scope to Iran-linked vessels [7]. In practice, the effect has been broader. With war-risk insurance premiums spiking 200% to 300% and several major insurers — including Norway's Gard and Skuld and the UK's NorthStandard — canceling coverage for Gulf transits entirely, most commercial shipping has simply stopped trying [8]. The blockade's reach exceeds its formal mandate.

The Price in Dollars per Barrel

The economic impact has been severe and measurable. Brent crude crossed $100 per barrel on March 8 for the first time in four years, peaked at $126 after the blockade announcement on April 13, then dropped 11% to roughly $96 following Iran's "open strait" declaration on April 17 [8][9]. WTI crude followed a similar trajectory, reaching $114.58 before pulling back to around $100 [10].

Source: FRED / EIA

Data as of Apr 13, 2026CSV

Beyond crude prices, the shipping industry has absorbed enormous costs. Supertanker freight rates to China doubled to over $400,000 per day [8]. War-risk insurance premiums jumped from a pre-crisis range of 0.02%–0.05% of vessel value to 5%–10% [8]. The Containerized Freight Index rose more than 35% year-over-year [8]. For a $100 million supertanker, the insurance increase alone represents a cost swing from $50,000 to $10 million per transit.

Source: Reuters / CNBC

Data as of Apr 17, 2026CSV

The strait normally handles roughly 20.3 million barrels of petroleum per day — about 25% of the world's maritime oil trade and 20% of global petroleum consumption [11]. An additional one-fifth of global LNG trade, primarily from Qatar, transits the same chokepoint [11]. The disruption of these flows has raised energy and agricultural input costs worldwide [3].

Asia's Exposure

The countries most vulnerable to a Hormuz closure are concentrated in Asia. Japan sources close to 75% of its crude oil imports through the strait; South Korea and India each depend on it for roughly 60% of their imports; and China, despite more diversified supply routes, still receives about 45% of its oil through Hormuz [12][13].

Source: EIA / Zero Carbon Analytics

Data as of Apr 17, 2026CSV

These countries' ability to withstand a prolonged disruption varies dramatically. Japan holds 175 days of strategic petroleum reserves — far more breathing room than India's roughly 10-day buffer [13]. China maintained approximately 1.2 billion barrels of crude stockpiles as of January 2026, enough for about 108 days of import cover at zero new inflows [13]. South Korea and Japan hold roughly 3.5 million and 4.4 million tons of LNG respectively, covering two to four weeks of demand [13].

No Asian government has formally protested the US blockade. Japan and South Korea, as US treaty allies, have remained publicly silent on the legal questions while privately scrambling to secure alternative supply [13]. India, the country with the thinnest reserves and the least capacity to absorb price shocks, has been the most vocal about wanting the strait reopened quickly but has stopped short of criticizing Washington directly [12].

Iran's Military Hand

Iran's capacity to disrupt the strait — separate from the question of whether it can hold a closure indefinitely — is substantial. The Islamic Revolutionary Guard Corps Navy fields more than 1,500 fast-attack craft, some capable of speeds exceeding 110 knots, designed for swarm tactics against larger warships [14]. Iran's anti-ship missile arsenal includes the Noor cruise missile (120–170 km range), the Khalij Fars anti-ship ballistic missile (300 km range), and the radar-homing Hormuz-2 variant [14].

The most asymmetric threat is Iran's mine inventory: an estimated 5,000 to 6,000 naval mines, one of the largest stockpiles in the world, ranging from simple contact mines to acoustic and magnetic influence mines [14]. The narrow geometry of the strait — 21 miles at its tightest point — means even a modest mining campaign could force commercial shipping to halt while mine-clearance operations, which are slow and dangerous, proceed [14].

Iran also operates three Kilo-class submarines and a growing fleet of Ghadir-class and Fateh-class midget submarines capable of torpedo attacks and mine-laying in shallow Gulf waters [14].

Independent military analysts assess that Iran could effectively disrupt traffic for days to weeks through mining and missile attacks, but sustaining a full closure beyond 72 hours against determined US mine-clearance and naval operations would be difficult [15]. The US Navy's challenge is the inverse: clearing the strait is achievable but keeping it open while the underlying conflict persists requires sustained, resource-intensive patrols. Pre-blockade, an average of 138 ships passed through daily — a volume that one Cornell University historian described as "almost impossible [for the Navy] to keep up with" [16].

The Legal Paradox

The legal situation is genuinely unusual, because neither the United States nor Iran has ratified the UN Convention on the Law of the Sea (UNCLOS). Iran signed but never ratified; the US never signed [7]. As one maritime law expert put it, "the rules which almost every country in the world has consented to can't serve as a basis of agreement" between the two principal antagonists [7].

The two sides operate under incompatible legal frameworks. The US argues that UNCLOS's "transit passage" regime — which permits continuous, unimpeded navigation through international straits — reflects customary international law binding on all states regardless of ratification [7]. Under this standard, neither Iran's closure nor the US blockade of Iranian ports would be lawful without a UN Security Council mandate.

Iran invokes pre-UNCLOS law, citing the 1949 Corfu Channel case and the 1958 Territorial Seas Convention, which grant only "innocent passage" — a weaker right that coastal states can suspend for security reasons [7]. Iran further claims status as a "persistent objector" to the transit passage standard, arguing it has consistently opposed the doctrine since UNCLOS negotiations began in 1982 [7].

The steelman of the Iranian legal position is straightforward: if any country were intercepting third-country vessels in an international waterway without a UN Security Council resolution, most international lawyers would call it a violation of customary international law. The US is applying standards to Iran that, if applied to itself, would be equally problematic [6][17]. Some European governments have reportedly reached this conclusion internally while maintaining public support for US policy, though none has said so on the record [6]. The UK has backed US action; other European states have been "reluctant to be seen as supporters of US aggressive policy towards Iran" [6].

The Diplomatic Gap

The failed Islamabad talks — the highest-level direct meeting between US and Iranian officials since the 1979 revolution — revealed how far apart the two sides remain [18].

Iran's 10-point proposal demanded the lifting of all primary and secondary sanctions, acceptance of continued nuclear enrichment, and recognition of Iranian control over the Strait of Hormuz [18]. The Trump administration's red lines included an end to all uranium enrichment, dismantlement of major enrichment facilities, and removal of Iran's stockpile of highly enriched uranium from the country [18].

The gap is structurally different from the 2015 JCPOA negotiations. Under that agreement, Iran accepted limits on enrichment to 3.67%, caps on centrifuge numbers, and IAEA inspections in exchange for sanctions relief [19]. The current US demands go further — zero enrichment versus constrained enrichment — while Iran's demands also go further, insisting on strait sovereignty that the JCPOA never addressed.

A specific sticking point was the timeline: the US reportedly sought a 20-year freeze on nuclear activities; Iran offered five years [20]. Vice President JD Vance said Iran chose "not to accept our terms" [18]. Iranian officials blamed the impasse on "excessive and unreasonable demands" that failed to respect Iran's "legitimate rights" [18].

Pakistan brokered the Islamabad talks, with China helping bring Iran to the table and Turkey and Egypt also mediating [18]. A next round is scheduled for Monday in Pakistan, though expectations remain low [21].

Who Is Driving the Policy — and Why

Defense Secretary Pete Hegseth has been the most visible proponent of the blockade, telling reporters it would last "as long as it takes" and urging Iran to pursue diplomacy [5]. Joint Chiefs Chairman Dan Caine warned that the US military remains "ready, if ordered or called upon, to resume combat operations with the same speed and precision" [22].

The stated objective is to force Tehran back to the negotiating table — economic pressure as a tool of compellence. But critics question whether the goal is behavior change, regime change, or something else entirely. Dana Stroul, a former senior Pentagon official now at the Washington Institute for Near East Policy, assessed that "this mission is difficult to execute alone and likely unsustainable over the medium to long-term" [15].

The House of Representatives recently rejected an effort to withdraw US forces from the Iran war, with Republican lawmakers voting to support the president's approach [23]. The vote suggests the blockade has sufficient domestic political support for now, but the combination of rising energy prices, strained military resources, and limited diplomatic progress creates a trajectory that several former officials have described as unsustainable without either escalation or concession.

What History Says About Naval Blockades

The historical track record for naval blockades achieving their stated political objectives is mixed at best.

The Cuban quarantine of 1962 is the clearest success case: the Soviet Union withdrew its missiles within days, though the resolution also required a secret US commitment to remove Jupiter missiles from Turkey [24]. The operation lasted 13 days.

The Iraq sanctions and naval embargo (1990–2003) tell a more cautionary story. Despite comprehensive UN-backed sanctions that caused significant economic damage, Saddam Hussein remained in power for 13 years, never complied with the demands that justified the embargo, and was ultimately removed only by a full-scale military invasion [25]. The blockade achieved containment but not compellence.

North Korea sanctions enforcement, including maritime interdiction, has failed to halt Pyongyang's nuclear weapons program. North Korea has consistently evaded sanctions through ship-to-ship transfers of petroleum products and coal [26].

Russia's attempted maritime restrictions on Ukrainian grain exports in 2022 were, as one historian noted, "quite quickly negotiated away," partly because Russia lacked the naval capacity to fully enforce them [16].

The pattern suggests that blockades work fastest when paired with credible diplomatic off-ramps and when the target state has a clear path to compliance. The current Iran standoff has neither: the diplomatic demands are maximalist on both sides, and the target state has shown willingness to absorb economic pain rather than capitulate on what it frames as sovereign rights.

What Comes Next

The ceasefire between Lebanon and Israel — a 10-day agreement announced April 17 — provided the context for Iran's "open strait" declaration [1]. But the ceasefire is temporary, the blockade continues, and the fundamental issues — Iran's nuclear program, the strait's legal status, the broader military conflict — remain unresolved.

The next round of talks in Pakistan, scheduled for April 21, will test whether either side has moved from its Islamabad positions [21]. The immediate question is whether the combination of Iran's symbolic opening of the strait and the Lebanon ceasefire can generate enough momentum for substantive negotiations before the ceasefire expires on April 27.

If it cannot, the standoff returns to its default trajectory: a US blockade that is effective but expensive and diplomatically isolating, an Iranian economy under severe strain but governed by leaders who show no signs of accepting Washington's terms, and a global energy market that has already priced in weeks of disruption but is unprepared for months of it.