The US military began blocking shipping traffic in and out of Iran's ports, a move that would prevent roughly two million barrels of Iranian oil a day from entering the world's markets, further tightening global supply.
Here are details on the blockade and its implications for oil markets.
What Was Announced?
After weekend peace talks in Islamabad between negotiators from the US and Iran ended without a deal, 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."
The US Central Command nL1N40W0DH said on Monday that unauthorised vessels entering or leaving the blockade would face "interception, diversion, and capture".
US forces would not impede freedom of navigation for vessels transiting the Strait of Hormuz to and from non-Iranian ports, 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.
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 an 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 either in transit or floating storage as of earlier this month, Kpler data showed.
Of that, roughly 100 million barrels were floating in waters off Malaysia and Indonesia, and China.
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, has remained largely halted despite a two-week ceasefire agreement between Washington and Tehran announced on April 7.
On Tuesday, a Chinese tanker nL1N40X02T carrying a cargo of methanol loaded at Hamriyah in the United Arab Emirates passed through the strait in what appeared to be the first transit of a tanker since the US blockade began, with two more vessels also crossing.
On Sunday, before the blockade began, two Pakistan-flagged tankers, Shalamar and Khairpur, entered the Gulf to load cargoes from the United Arab Emirates and Kuwait; a third ship, the Liberia-flagged very large crude carrier (VLCC) Mombasa B, also transited the strait on Sunday and was ballasting in the Gulf.
The Malta-flagged VLCC Agios Fanourios I, which tried to pass through the strait on Sunday to load Iraqi crude destined for Vietnam, turned back and was anchored near the Gulf of Oman.
Some 187 laden tankers carrying 172 million barrels of crude oil and refined products were inside the Gulf as of April 7, according to Kpler.
Which Importers Are Most Affected?
Before the war, most Iranian oil exports were shipped to China, the top global crude importer.
Last month, the US unveiled a sanctions waiver that has enabled other buyers, including India, to import Iranian oil.
India was set to receive its first crude shipment from Iran nL8N3ZX1Y1 in seven years this week, ship tracking data from LSEG and Kpler showed.
Before the war, roughly 20 per cent of global oil and natural gas exports were shipped through the Strait of Hormuz, with most cargoes headed to Asia, the largest importing region.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)
