The United States says a US Navy ship has "destroyed" an Iranian drone in the Strait of Hormuz after it threatened the vessel, a claim Iran promptly denied.
In remarks at the White House on Thursday, US President Donald Trump said the drone had flown to within 1,000 metres of the USS Boxer and had ignored "multiple calls to stand down".
"This is the latest of many provocative and hostile actions by Iran against vessels operating in international waters. The US reserves the right to defend our personnel, facilities and interests," Trump said.
"The drone was immediately destroyed," he added.
Abbas Araghchi, Iranian deputy foreign minister, dismissed the claim in a Twitter post on Friday.
"We have not lost any drone in the Strait of Hormuz nor anywhere else. I am worried that USS Boxer has shot down their own UAS [Unmanned Aerial System] by mistake!" he wrote.
Hours earlier, Iran's Foreign Minister Mohammad Javad Zarif, who was in New York for meetings at the United Nations, said he had "no information about losing a drone".