What is a naval blockade and how would it work?

After weekend peace talks in Islamabad between negotiators from the U.S. and Iran ended without a deal, President Donald Trump said the U.S. Navy "will begin the process of BLOCKADING any and all ships trying to enter, ​or leave, the Strait of Hormuz."

 

The U.S. military's Central Command later said the blockade would only apply to ships going to or from Iran, ​including all Iranian ports on the Gulf and Gulf of Oman. U.S. forces would not impede freedom of navigation ⁠for vessels transiting the Strait of Hormuz to and from non-Iranian ports and additional information would be provided, it said.

Iran's Revolutionary Guards responded to Trump ​by warning that military vessels approaching the strait would be considered a ceasefire breach and dealt with harshly and decisively.

Retired Admiral Gary Roughead, a former chief ​of U.S. naval operations, cautioned that Iran could fire on ships in the Gulf or attack the infrastructure of Gulf states that host U.S. forces.

WHAT IS THE IMPLICATION FOR OIL FLOWS?

Blocking Iranian shipments would disconnect a significant source of oil from the world's markets. Iran exported 1.84 million barrels per day (bpd) of crude in March and has shipped 1.71 ​million bpd thus far in April, compared with a full-year average of 1.68 million bpd in 2025, according to Kpler data.

However, a surge in Iranian ​output before the war started on February 28 has led to near-record levels of Iranian oil loaded on ships, with more than 180 million barrels floating as of ‌earlier this ⁠month, according to Kpler data.

WHAT ABOUT OIL FLOWS FROM OTHER GULF PRODUCERS?

Shipping traffic through the Strait of Hormuz, which has been severely curtailed by an Iranian blockade since the start of the war, remains nearly halted despite last week's two-week ceasefire agreement between Washington and Tehran.

Oil tankers were steering clear of the strait on Monday.

WHAT IS THE IMPLICATION FOR OIL FLOWS?

Blocking Iranian shipments would disconnect a significant source of oil from the world's markets. Iran exported 1.84 million barrels per day (bpd) of crude in March and has shipped 1.71 ​million bpd thus far in April, compared with a full-year average of 1.68 million bpd in 2025, according to Kpler data.

However, a surge in Iranian ​output before the war started on February 28 has led to near-record levels of Iranian oil loaded on ships, with more than 180 million barrels floating as of ‌earlier this ⁠month, according to Kpler data.

WHAT ABOUT OIL FLOWS FROM OTHER GULF PRODUCERS?

Shipping traffic through the Strait of Hormuz, which has been severely curtailed by an Iranian blockade since the start of the war, remains nearly halted despite last week's two-week ceasefire agreement between Washington and Tehran.

Oil tankers were steering clear of the strait on Monday.

WHICH IMPORTERS ARE MOST AFFECTED?

Before the war, most Iranian oil exports were shipped to China, the top global crude importer. Last month, the ⁠U.S. unveiled ​a sanctions waiver that has enabled other buyers, including India, to import Iranian oil.

India is set ​to receive its first crude shipment from Iran in seven years this week, ship tracking data from LSEG and Kpler showed on Wednesday.

Before the war, roughly 20% of global oil and natural ​gas exports were shipped through the Strait of Hormuz, with most cargoes headed to Asia, the largest importing region.

-Reuters