Iran's top joint military command announced on Saturday that the Strait of Hormuz would be closed again, citing what it described as US violations of the recently signed US-Iran memorandum of understanding and continuing Israeli military operations in southern Lebanon.
According to statements carried by Iranian state media and reported by the Associated Press, the military command said the closure was a response to Washington's failure to implement commitments under the agreement and Israel's breaches of a ceasefire in Lebanon.
The statement described the move as a "first step" and warned that further measures could follow if what it called aggression continued. Iran's Islamic Revolutionary Guard Corps also warned vessels against approaching the strait, saying their security could be at risk.
The announcement came as violence escalated in southern Lebanon. Lebanese authorities said Israeli strikes killed at least 16 people, including two children, while Hezbollah accused Israel of repeatedly violating the ceasefire. Israel said Hezbollah had fired more than 50 projectiles overnight, prompting retaliatory strikes on militant targets.
Lebanon's health ministry said the death toll from the latest Israel-Hezbollah conflict has now exceeded 4,000.
The renewed closure threatens a diplomatic breakthrough reached earlier this week under which Iran and the United States agreed to reopen the Strait of Hormuz and begin negotiations on a broader settlement covering Iran's nuclear programme and sanctions relief.
The strait, which carries roughly one-fifth of global oil and liquefied natural gas shipments, had reopened only days earlier under the agreement.
Despite Iran's announcement, the US military said commercial shipping was continuing through the waterway. It reported that 55 merchant vessels carrying more than 17 million barrels of oil and other cargo transited the strait on Saturday.
Meanwhile, Iran and the United States are still preparing for further talks in Switzerland. Iranian Foreign Minister Abbas Araghchi and other senior officials are expected to travel for the discussions, while US Vice President JD Vance said he expects to join negotiations within days.