How strikes on Iran put focus on the Strait of Hormuz

TEHRAN - US President Donald Trump has

followed through on a threat to attack Iran

after talks failed to secure a deal to curb the country’s nuclear program. For Tehran, one option for retaliation is to try to block or effectively close the Strait of Hormuz. 

This narrow waterway at the mouth of the Persian Gulf handles about a quarter of the world’s seaborne oil trade. If Iran were to deny access to the giant tankers that ferry oil and gas from the Middle East to China, Europe, the US and other major energy consumers, the disruption would trigger a spike in oil prices and potentially destabilise the global economy.

Oil already hit a six-month high in February amid growing speculation that Mr Trump could order military strikes. 

What’s the significance of the Strait of Hormuz? 

With Iran to its north and the United Arab Emirates and Oman to its south, the Strait of Hormuz connects the Persian Gulf to the Indian Ocean.

It is an essential passage for global oil trade. Most suppliers around the Persian Gulf have no other sea route for their exports. Tankers hauled about 16.7 million barrels a day of crude and condensate through the strait in 2025, according to data compiled by Bloomberg. Saudi Arabia, Iraq, Kuwait, the UAE and Iran all ship oil through Hormuz and the majority of their cargoes are destined for Asia.

The waterway is also crucial for the liquefied natural gas market. Nearly a fifth of the world’s supply of LNG - mostly from Qatar - passed through this channel last year.

The Strait of Hormuz is almost 161km long and 33km wide at its narrowest point. The shipping lanes in each direction are just two miles wide. The shallow depth of the waterway makes ships vulnerable to mines, while the proximity of the strait to land - Iran, in particular - leaves vessels open to attack from shore-based missiles or interception by patrol boats and helicopters.

Can Iran really block the Strait of Hormuz?

Under the United Nations Convention on the Law of the Sea, countries can exercise sovereignty up to 22km from their coastline - a smaller distance than the narrowest point of the Strait of Hormuz. They must allow “innocent passage” of foreign vessels through these territorial waters and must not impede “innocent” or “transit passage” through straits used for international navigation. While Iran signed this treaty in 1982, it hasn’t been ratified by the nation’s parliament.

The Iranian government has said during previous periods of heightened geopolitical tension that it has the ability to impose a naval blockade. It has never followed through on threats to completely shut off access to the strait - a move that would likely be met with a strong response from Western navies patrolling the area, in particular the US.

Iran could cause severe disruption without a single one of its warships leaving port. It has a number of options thanks to its coastline along the waterway. These range from lower-impact harassing of ships with small, fast patrol boats, to more extreme alternatives, such as attacking tankers with missiles and drones so it becomes too dangerous for commercial vessels to venture through the strait. Iran could also lay sea mines, although the resulting risk to its own ships may make such a move less likely.

Modern-day vessels are vulnerable to the jamming of global positioning system signals - a tactic that’s increasingly being used by state and non-state actors around the world to disrupt navigation. Thousands of ships suffered disruption in and around the Strait of Hormuz during the Iran-Israel conflict last June.

How would disruption in the Strait of Hormuz affect the oil market? 

If it becomes dangerous for ships to traverse the strait, they may only make the journey in convoys under the protection of Western navies. This would slow traffic but shouldn’t significantly impact oil global supply.

A full closure of the waterway for more than a few days is a nightmare scenario for energy markets. Kpler Ltd. senior crude analyst Muyu Xu estimated in June that Iran blocking the strait for just one day could cause oil prices to surge as high as US$120 (S$151) to US$150 a barrel. Brent crude, the international benchmark, had averaged US$66 a barrel year-to-date as of Feb 20.

Closing the Strait of Hormuz would quickly hit Iran’s own economy as it would be unable to export its petroleum. Disruption to oil flows out of the Middle East would also risk antagonising China, the biggest buyer of Iranian crude and a critical partner that’s used its veto power at the UN Security Council to shield Iran from Western-led sanctions or resolutions.

Who relies most on the Strait of Hormuz?

Saudi Arabia exports the most oil through the waterway. However, it can divert shipments by using a 1,200km pipeline that runs across the kingdom to a terminal on the Red Sea, where the oil can be loaded onto vessels for onward transport. The East-West Pipeline is able to carry 5 million barrels of crude a day.

The UAE can likewise bypass the Strait of Hormuz to a certain degree, by leaning on a pipeline that runs from its oil fields to a port along the Gulf of Oman. The Habshan-Fujairah pipeline has the capacity to move 1.5 million barrels of crude a day.

Iraq has a pipeline that runs through Turkey to the Mediterranean coast and was reopened last year. But this can only carry oil pumped from fields in the north of the country, so nearly all of its crude exports are shipped by sea from the port of Basra and pass through the Strait of Hormuz. Kuwait, Qatar and Bahrain have no option but to ship their oil through the waterway.

Iran also depends on the strait to export its oil. More of the country’s crude was shipped through the waterway in 2025 than at any time since 2018, according to vessel tracking data compiled by Bloomberg.

How have the US and allies responded to threats to Hormuz shipping? 

During the 1980-88 Iran-Iraq war, strikes on oil facilities escalated to both sides attacking merchant vessels in the Persian Gulf, in what came to be known as the Tanker War. The US navy resorted to escorting Kuwaiti ships carrying Iraqi oil through the Gulf.

In 2019, countries including the UK, Saudi Arabia and Bahrain joined a US-led coalition known as the International Maritime Security Construct to secure sea lines in the Middle East vital to oil shipping. This followed a series of attacks on vessels and onshore facilities that some coalition members blamed on Iran.

Since late 2023, much of the focus on protecting shipping has switched away from the Strait of Hormuz and to the southern Red Sea. This has been in response to attacks by the Iran-backed Houthi militants in Yemen, who have targeted ships in the Bab el-Mandeb Strait that connects the Red Sea to the Gulf of Aden and Indian Ocean.

During the most recent US-Iran tensions, vessels have increased their speed through the Strait of Hormuz to minimise the time they’re at risk, while the US has advised American-flagged ships to stay as far away as possible from Iranian waters when navigating the waterway. Separately, a US F-35C warplane shot down an Iranian drone in early February as the unmanned aircraft “aggressively approached” the USS Abraham Lincoln aircraft carrier with “unclear intent,” according to US Central Command. BLOOMBERG