Live updates: Follow the latest news on Iran war
US President Donald Trump said the US would start escorting foreign vessels out of the Strait of Hormuz from Monday under a new "humanitarian" initiative.
In a post on Truth Social, Mr Trump said countries not involved in the Middle East conflict had asked Washington for help to free ships stranded in the important waterway.
In response, a senior Iranian official warned that the Islamic republic would treat any such move as a violation of the ceasefire.
“Any American intervention in the process of the new Strait of Hormuz maritime system will be considered a violation of the ceasefire,” Ebrahim Azizi, head of Iran’s parliament National Security Commission, wrote on X.
The United Kingdom Maritime Trade Operation, based in Dubai, reported a vessel had been struck "78 nautical miles north of Fujairah" in the Strait of Hormuz. A map showed the site closer to Musandam in Oman.
UKMTO said the ship was "hit by an unknown projectile", but that the crew was safe and the vessel was still operational.
The US operation could lead to an open conflict between Iran and American forces, but Mr Trump said neutral ships must be allowed safe passage.
“They are merely neutral and innocent bystanders. For the good of Iran, the Middle East and the United States, we have told these countries that we will guide their ships safely out of these restricted Waterways, so that they can freely and ably get on with their business,” he wrote.
Centcom said the effort, dubbed "Project Freedom" would include guided-missile destroyers, over 100 land- and sea-based aircraft, drones and 15,000 service members.
“Our support for this defensive mission is essential to regional security and the global economy as we also maintain the naval blockade,” said Centcom chief Admiral Brad Cooper in a statement.
Mr Trump warned that any interference with the operation would be met with force.
“If, in any way, this humanitarian process is interfered with that interference will, unfortunately, have to be dealt with forcefully,” he said.
The operation would begin on Monday morning local time in the Middle East. Mr Trump said US officials were holding “very positive discussions” with Iran.
He said the ships would be able to resume normal operations, and that many vessels were low on food and essential supplies.
Details of the plan remain unclear, but Axios reported it may stop short of direct US Navy escorts, with warships instead staying nearby to intervene if needed and guiding commercial vessels along safer, mine-free routes.
Trump's announcement comes a day after he said he would study Iran's 14-point proposal, which calls for an end to the war in 30 days.
He earlier said he "can't imagine" that the proposal, which includes sanctions relief and an American withdrawal from the region, would be acceptable.
In a post on Truth Social, he wrote that Iran had “not yet paid a big enough price for what they have done to humanity, and the world, over the last 47 years.”
