Iranian state media said on Tuesday that parts of the strategic Strait of Hormuz will be closed for a few hours due to "security precautions" for shipping safety.
This comes as Iran's Islamic Revolutionary Guard Corps (IRGC) conducts military drills in the waterway amid rising tensions with the US.
About 20 to 30 per cent of the world's total daily oil consumption – more than 20 million barrels per day – pass through the Strait of Hormuz, along with cargo to and from the Gulf states.
"Today, in the smart control exercise of the Strait of Hormuz, to observe safety and navigation principles, parts of the Strait of Hormuz will be closed for a few hours," said Iran's Fars news agency.
It quoted the commander of the IRGC Navy as saying "the weapon that reaches the battlefield on the day of war is different from what is shown in the exercise".
The naval military drills come amid simmering tensions and fears of renewed conflict despite continuing nuclear talks between Tehran and Washington. The US has warned that it would attack Iran if a deal is not reached. It has significantly ramped up its naval deployments in the Middle East, including by sending the USS Abraham Lincoln aircraft carrier group to within striking distance of Iran.
The IRGC drills in the Strait of Hormuz appeared designed to send a warning to Washington about Iran's ability to retaliate at sea to any strikes.
Iranian state television broadcast images from the exercise, and showed military ships launching missiles aimed at “destroying enemy aerial targets,” the reporter said.
The launches include the Sayyad 3F surface to air missile, which has a range of 150km, he added.
Upgrades to missile warheads means that the "intensity of destruction and damage to enemy [naval] destroyers is greater than before. New guidance systems mean these missiles can attack their targets from any direction and location,” he added.
The US and Iran resumed indirect nuclear negotiations in Geneva on Tuesday.
The talks, mediated by Oman, are aimed at reaching a new nuclear agreement. The US wants Iran to end any uranium enrichment, while Tehran – despite losing key nuclear sites to US strikes and the war with Israel last year – insists on preserving enrichment capability.
“We are here with good intentions and seriousness. We are result-orientated. The time is very important for us, it is crucial,” Iranian Foreign Ministry spokesman Esmaeil Baghaei told state TV.
He said Iran hopes that Washington will demonstrate “the same level of seriousness and good intention” as the talks proceed.
What is the Strait of Hormuz?
It is a narrow channel, about 35km wide at the narrowest point, located between Oman and Iran. It is one of the most important waterways in the world as it links the Middle East’s crude oil producers with other key markets, making it vital to the global energy supply.
Despite threats, the politically sensitive strait has never been closed by Iran. Saudi Arabia, the world's largest exporter of crude, moves more hydrocarbons through the strait than any other country in the Gulf.
“There is no alternative route to the Strait of Hormuz," Jakob Larsen, chief safety and security officer at shipping firm Bimco, told The National earlier this week.
"We have seen around a 50 per cent drop in numbers of ships going through the Bab Al Mandeb strait and the Red Sea due to Houthi attacks in connection with the Israeli military operation in Gaza. These ships have indeed rerouted south of Cape of Good Hope.”
