How a US naval blockade of Iran could affect oil flows

A fresh US military move at Iran’s ports is set to squeeze global oil supplies, threatening to keep roughly two million barrels a day of Iranian crude off the market and raising the stakes for energy traders already on edge.

Below is a closer look at the blockade and what it could mean for oil flows worldwide.

What was announced?

After weekend peace talks in Islamabad between negotiators from the US and Iran ended without an agreement, President Donald Trump said the US Navy “will begin the process of BLOCKADING any and all ships trying to enter, or leave, the Strait of Hormuz.”

Iran’s Revolutionary Guards fired back with a warning to Mr Trump, saying military vessels nearing the strait would be treated as violating the ceasefire and met harshly and decisively.

What is the implication for oil flows?

Stopping Iranian shipments would cut off a major stream of oil to global markets. Iran exported 1.84 million barrels per day (bpd) of crude in March and has shipped 1.71 million bpd so far in April, versus an average of 1.68 million bpd in 2025, according to Kpler data.

At the same time, a jump in Iranian production before the war began on 28 February left unusually large volumes of crude already loaded at sea. More than 180 million barrels were either in transit or held in floating storage earlier this month, Kpler data showed.

Of that total, about 100 million barrels were floating in waters off Malaysia and Indonesia, and China.

Oil flows from other Gulf producers?

Traffic through the Strait of Hormuz has been heavily reduced by an Iranian blockade since the war began, and movement has stayed mostly stalled despite a two-week ceasefire between Washington and Tehran announced on 7 Apri.

A Chinese tanker carrying methanol loaded at Hamriyah in the United Arab Emirates moved through the strait today in what appeared to be the first tanker transit since the US blockade started, while two other vessels also crossed.

On Sunday, before the blockade took effect, two Pakistan-flagged tankers, Shalamar and Khairpur, entered the Gulf to load cargoes from the United Arab Emirates and Kuwait. A third vessel, the Liberia-flagged very large crude carrier (VLCC) Mombasa B, also passed through the strait on Sunday and was ballasting in the Gulf.

The Malta-flagged VLCC Agios Fanourios I, which attempted to transit the strait on Sunday to load Iraqi crude bound for Vietnam, later turned back and anchored near the Gulf of Oman.

As of 7 April, 187 laden tankers carrying 172 million barrels of crude oil and refined products were inside the Gulf, according to Kpler.

Which importers are most affected?

Before the war, the bulk of Iran’s oil exports went to China, the world’s largest crude importer. Last month, the US announced a sanctions waiver that allowed other buyers, including India, to import Iranian oil.

India was due to receive its first crude shipment from Iran in seven years this week, according to ship-tracking data from LSEG and Kpler.

Before the war, about 20% of global oil and natural gas exports moved through the Strait of Hormuz, with most of those shipments heading to Asia, the biggest importing region.