The U.S. military said it would block maritime traffic entering and exiting Iranian ports starting at 10:00 a.m. ET (2:00 p.m. GMT) on Monday, a move that would prevent about two million barrels of Iranian oil per day from entering global markets, tightening global supplies.
Here are details on the planned blockade and its implications for oil markets.
What was announced?
After weekend peace talks in Islamabad between U.S. and Iranian negotiators ended without a deal, President Donald Trump said the U.S. Navy “will begin the process of BLOCKING all vessels attempting to enter or exit the Strait of Hormuz.”
The US military’s Central Command later said the blockade would only apply to ships going to or from Iran, including all Iranian ports in the Gulf and the Gulf of Oman. US forces will not impede the freedom of navigation of ships transiting the Strait of Hormuz to and from non-Iranian ports and additional information will be provided, it said.
Iran’s Revolutionary Guard responded to Trump by warning that military vessels approaching the strait would be considered a violation of the ceasefire and would be dealt with harshly and decisively.
Retired Adm. Gary Roughead, former chief of U.S. naval operations, warned that Iran could fire on ships in the Gulf or attack infrastructure in Gulf states that host U.S. forces.
What is the implication for oil flows?
Blocking Iranian shipments would disconnect a major source of oil from 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, compared to an annual average of 1.68 million bpd in 2025, according to Kpler data.
However, a surge in Iranian production before the war began on Feb. 28 led to near-record levels of Iranian oil loaded onto ships, with more than 180 million barrels floating at the start of the month, according to Kpler data.
What about oil flows from other Gulf producers?
Maritime traffic crossing the Strait of Hormuz, which has been severely reduced by the Iranian blockade since the start of the war, remains virtually halted despite the two-week ceasefire agreement reached last week between Washington and Tehran.
Oil tankers avoided the strait on Monday.
On Sunday, two Pakistani-flagged oil tankers, Shalamar and Khairpur, entered the Gulf to load cargoes from the United Arab Emirates and Kuwait; A third ship, the Liberian-flagged Very Large Crude Carrier (VLCC) Mombasa B, also transited the strait earlier on Sunday and was ballast in the Gulf.
Another VLCC, the Maltese-flagged Agios Fanourios I, which was trying to pass through the strait on Sunday to load Iraqi crude destined for Vietnam, turned around and anchored near the Gulf of Oman.
On Saturday, three fully loaded supertankers crossed the Strait of Hormuz aboard what appears to be the first ships to leave the Gulf since the U.S.-Iran ceasefire agreement.
According to Kpler, some 187 loaded tankers carrying 172 million barrels of crude oil and refined products were in the Gulf as of Tuesday.
Which importers are most affected?
Before the war, most of Iran’s oil exports were shipped to China, the world’s largest importer of crude. Last month, the United States unveiled a sanctions waiver that allowed other buyers, including India, to import Iranian oil.
India is expected 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, about 20 percent of global oil and natural gas exports passed through the Strait of Hormuz, with most cargoes destined for Asia, the largest importing region.
