Iran's Revolutionary Guard has halted two Qatar liquefied natural gas tankers that had been heading towards the Strait of Hormuz and instructed them to hold position without explanation, a source told Reuters.
Iran had permitted the vessels to transit the strait under an agreement reached with the United States last week via Pakistani mediation, said the source who had been briefed on the agreement and spoke on condition of anonymity.
"This was part of an arrangement negotiated as part of talks spearheaded by Pakistan last week," the source said on Monday.
Both ships were positioned off the coast of the United Arab Emirates on Monday evening and had not transited Hormuz, ship-tracking data showed.
Had the vessels successfully crossed the strait, they would have been the first transit of LNG cargoes through the waterway since the start of the US-Israeli war with Iran on February 28.
The conflict, which began with US and Israeli strikes on Iran, has killed thousands and damaged economies by driving up oil prices.
Tanker traffic through the Strait of Hormuz, a route that carries about a fifth of global oil and LNG flows, has been effectively closed by the fighting and retaliatory attacks.
US President Donald Trump said on March 26 that Iran had agreed to let 10 oil tankers transit the Strait of Hormuz as an apparent goodwill gesture in negotiations.
"They said, to show you the fact that we're real and solid and we're there, we're going to let you have eight boats of oil, eight boats, eight big boats of oil," Trump said.
"I guess they were right, and they were real, and I think they were Pakistani-flagged. It ended up being 10 boats."
Data from analytics firms Kpler and LSEG showed the two Qatari vessels, Al Daayen and Rasheeda, loaded their cargoes in late February.
The vessels were loaded with LNG from Ras Laffan, Qatar. They had been moving eastward towards the strait but turned back on Monday morning, ship-tracking data showed.
The two vessels changed course signals on Monday afternoon.
The Al Daayen began signalling Ras Laffan as its destination after previously indicating a destination of Pakistan, while the Rasheeda switched to signalling “for orders", a generic placeholder, from Port Qasim, in Pakistan. Earlier on Monday, the Al Daayen had been signalling for China, the data showed.
Kpler data showed both tankers as controlled by QatarEnergy.
QatarEnergy did not immediately respond to a Reuters request for comment about Iran's Revolutionary Guards having stopped the ships.
Previously, a Japanese LNG tanker, the Sohar LNG, managed to cross the strait, its joint owner, Mitsui OSK Lines, said on Friday.
The tanker, however, was empty, and a company spokesperson declined to disclose when the passage took place or whether any negotiations were involved.
Qatar is the world's second-largest exporter of LNG, with shipments mostly going to buyers in Asia. Iranian attacks knocked out 17 percent of Qatar's LNG export capacity, with repairs expected to sideline 12.8 million tonnes per year of the fuel for three to five years.
