How U.S. and Iranian Blockades Are Disrupting Strait of Hormuz Shipping

Iran’s pressure is broader in practical effect. A U.S. Maritime Administration advisory says Iran continues to threaten and conduct strikes on commercial vessels transiting the Persian Gulf, Strait of Hormuz, and Gulf of Oman, and that risks to commercial shipping remain high in those areas ^[1]. Separate reporting says Iran has maintained restrictions around the strait and has moved to formalize control by creating an agency to vet and tax vessels seeking passage ^[6][9].

That combination leaves shipping companies caught between two constraints: U.S. restrictions on Iran-linked port traffic and Iranian controls or threats around the strait itself ^[6][8][14].

Traffic is muted, not zero

Ship-tracking reports show that Hormuz traffic has continued at very low levels rather than stopping entirely. On April 21, only three ships were reported to have passed through the strait in the previous 24 hours ^[9]. On April 27, at least seven ships, mainly dry bulk vessels, crossed in the previous 24 hours, which was described as consistent with muted activity in preceding days ^[5].

The bottleneck is still severe. Associated Press reporting carried by Audacy said hundreds of commercial ships were bottled up in the Persian Gulf and unable to reach the open sea after Iran created its vetting-and-taxing agency for passage through the strait ^[6]. Separately, the Los Angeles Times reported that the U.S. naval blockade of Iranian ports had forced 48 commercial vessels to turn back by May 2 ^[8].

The result is not a clean binary of open or closed. Hormuz remains passable for some traffic, but it is no longer functioning like a normal, reliable global shipping lane ^[5][6][9].

The main commercial impacts

1. Delays, turnbacks, and vessel backlogs

The clearest impact is operational: vessels are waiting, attempting limited transits, or turning back. The reported counts of three and seven daily transits in late April show sharply muted movement, while reports of hundreds of ships bottled up in the Gulf indicate a broader backlog ^[5][6][9].

2. Higher security exposure

The security environment is central to the disruption. The U.S. Maritime Administration advisory says Iran continues to threaten and conduct strikes on commercial vessels in the Persian Gulf, Strait of Hormuz, and Gulf of Oman, and notes that Iranian forces have historically used small boats and helicopters in boarding operations and attempted to force commercial vessels into Iranian territorial waters ^[1].

For shipowners, charterers, and crews, that means voyage planning is no longer just a question of distance and fuel. It now includes the risk of attack, boarding, forced diversion, or escalation while transiting a narrow chokepoint ^[1].

3. Insurance and legal uncertainty

Marine-insurance and shipping-law risk has increased because operators face overlapping and potentially conflicting controls. Shipping-law analysis has described the Gulf situation as one in which Iran asserts control over passage through the Strait of Hormuz while the U.S. has announced a blockade of maritime traffic entering and exiting Iranian ports ^[4].

The exact cost increase will vary by vessel, cargo, route, insurer, and charter terms. The available sources support the conclusion that risk and uncertainty have risen, but they do not establish a single current war-risk premium or universal surcharge ^[1][4].

4. Sanctions risk for payments to Iran

A major commercial complication is whether companies can pay Iran for safe passage or clearance. The Los Angeles Times reported that the U.S. warned shipping companies they could face sanctions for paying Iran to ensure safe passage through the Strait of Hormuz ^[8].

That creates a difficult compliance problem: a ship may face Iranian demands or controls to move through the strait, while also facing U.S. sanctions exposure if it pays Iran for passage ^[6][8].

5. Energy-market disruption

Hormuz matters because it is a critical energy chokepoint. Reporting cited in the source set says the strait had typically handled roughly one-fifth of the world’s oil and liquefied natural gas supply ^[9]. When traffic falls to crisis levels, the effect is not limited to Gulf ports; it can disrupt cargo scheduling, tanker availability, and energy-market expectations far beyond the region ^[5][9].

Which vessels are most affected?

The most directly affected vessels are those entering or leaving Iranian ports, because that is the stated focus of the U.S. blockade ^[14]. Ships serving non-Iranian Gulf ports are not supposed to be blocked by the U.S. under CENTCOM’s stated policy, but they still face the broader risks created by Iranian restrictions, attack threats, and uncertainty around passage ^[1][6][14].

Vessels already inside the Persian Gulf may be especially exposed if they need to exit through Hormuz but cannot secure a safe, legally compliant, and commercially viable passage ^[6][8]. Energy cargoes are also highly exposed because of the strait’s role in oil and LNG flows ^[9].

What remains uncertain

The source record is uneven and the situation is moving quickly. Official U.S. sources define the U.S. blockade and maritime threat guidance ^[1][14]. Traffic counts, Iranian control measures, vessel backlogs, and sanctions-warning details come from news, industry, or wire-service reporting and should be treated as a snapshot of a developing crisis ^[5][6][8][9].

The practical takeaway for commercial shipping is clear: Hormuz is not fully closed, but it is operating under extreme disruption. For many operators, the difference between a formal closure and a partial one may matter less than the day-to-day reality of delayed voyages, uncertain clearance, higher risk scrutiny, possible sanctions exposure, and unreliable transit windows ^{[1][5][6][8][14]}.