DUBAI: Iran announced the closure of the Strait of Hormuz on Sunday (Jul 12) "until further notice" after firing on a vessel it said was taking an unauthorised route, prompting US retaliatory strikes that further undermine an already shaky ceasefire.The closure of the strategic waterway marks the latest escalation in a dispute that has become one of the main roadblocks to a final US-Iran agreement.Tehran insists it will regulate shipping through Hormuz, while Washington demands unrestricted navigation through a route that carries roughly a fifth of global oil and liquefied natural gas trade.Iran's Revolutionary Guards said Sunday they struck and stopped a vessel ignoring repeated instructions to use an approved shipping corridor, according to a statement carried by state news agency IRNA."Following this incident ... the Strait of Hormuz will be closed until further notice and until the end of American interventions in this region and no vessels will be allowed to pass through," the Guards said.Although Iran called the strike on the ship "warning shots", the US military said Tehran "blatantly attacked" a Cyprus-flagged container ship transiting the Strait of Hormuz.A crew member was missing and the vessel had been disabled by fire and damage to its engine room, US Central Command (CENTCOM) said."In response, the United States is imposing a heavy cost by continuing to degrade Iran's ability to attack civilian mariners and commercial ships freely transiting the strait," it said on X.The strikes, which began at 7.15pm Saturday in Washington, were the third round carried out this week and were taking place at the direction of President Donald Trump, CENTCOM said.US Defence Secretary Pete Hegseth said simply: "Iran made a poor choice. Now they pay."CRITICAL STRAITEarlier strikes by Tehran on vessels in the strait had triggered exchanges of fire between Iran and the United States, sparking heated rhetoric between the adversaries.The tensions threatened an interim agreement aimed at ending the Middle East war, which broke out in late February with massive US-Israeli strikes that killed former supreme leader Ali Khamenei.A key roadblock to a final agreement is the future of the Strait of Hormuz, which Iran closed to commercial shipping during the war.The waterway is a key conduit for oil and gas exports out of the energy-rich Gulf, and its closure has heavily impacted the world economy.Iran insists on controlling the passage of ships and has announced plans to charge fees, saying there will be no return to the free navigation of the pre-war era - a stance Washington has rejected.Under customary international law, states are not generally permitted to charge tolls on straits used for international navigation.