Iran on Sunday said it closed the Strait of Hormuz after a vessel traveled on an unapproved route and was struck, warning that any retaliation over the incident would be met with a "severe response".
"A vessel that had jeopardised maritime security by switching off its systems was struck and brought to a halt," the Navy of Iran's Revolutionary Guard Corps said in a statement, without giving any details about the ship.
The statement said several ships attempted to move through the waterway on an "unauthorised route" and disregarded warnings to correct their course.
The strait, the IRGC said, was closed "until further notice" and until "the end of US interference in this region." Acts of aggression against Iran "will be met with a severe response, and new enemy bases in the region will be targeted," the Navy said.
The United States i s demanding that Iran publicly state it will stop attacks on ships in the strait, and that all lanes will be open with no tolls through the waterway, senior US officials told reporters on Friday.
US President Donald Trump said on Friday the US and Iran had agreed to continue talks despite an escalation of hostilities this week, while also declaring an end to the ceasefire.
A senior Iranian source told Reuters that Iran, the US, Qatar and Pakistan had agreed to negotiate in a call that mediators were trying to arrange for Saturday while Iran's Foreign Minister Abbas Araqchi was in Oman. It was not immediately clear whether the efforts were successful.
Araqchi and Omani Foreign Minister Sayyid Badr Albusaidi met in Oman to exchange "views on appropriate mechanisms for the safe passage of ships through the Strait of Hormuz," according to a statement from the Iranian foreign minister.
Oman's state news agency later said that Omani and Iranian negotiators would continue talks "at the technical and political levels."
Oman is helping to mediate an end to a war that has destabilised the Gulf and raised prices around the world since the US and Israel launched airstrikes on Iran on 28 February.
About a fifth of the world's oil supply transited through the Strait of Hormuz before the war, and Iran's effective blockade of the waterway has caused energy prices to surge, fuelling global inflation.
CNN reported on Saturday that Oman made a draft proposal for the strait, including free navigation through its southern corridor in Omani territorial waters.
The plan called for vessels transiting the northern corridor through Iranian territorial waters to obtain prior approval from Iran, although no tolls would be imposed, CNN said.
The White House and State Department did not immediately respond to requests for comment on the CNN report.