Iran said the video proved nothing and that it was being made into a scapegoat. “These accusations are alarming,” Foreign Ministry spokesman Abbas Mousavi said.
It later emerged that a US MQ-9 drone had been tracking Iranian fast boats as they closed in on the tankers.
Iranian forces tried to shoot the drone out of the sky but their surface-to-air missile missed.
A US State Department source said President Trump’s aim continues to be to force Tehran into a new “comprehensive deal” in return for lifting crippling sanctions.
However, he added: “We’ve made it clear that we will defend our forces and interests.”
Iran has angered the US by its military involvement in Iraq, Yemen, Syria and Lebanon, and by threatening international waterways.
It has previously suggested it could block the Strait of Hormuz, the main route out for Middle Eastern oil, if its own exports were halted.
Following the attack on the two tankers, Tehran announced