Ever since Donald Trump withdrew the US from a multinational nuclear accord with Iran the two countries have been involved in a spiraling dispute.
In recent days the tension has moved beyond tweets and fiery speeches and focused on the world's busiest oil shipping route, the Strait of Hormuz.
After a series of incidents in which tankers passing the Iranian coast were damaged, the US has pointed the finger at Tehran, which angrily denies the accusations.
The downing of a US drone by an Iranian missile system has raised the stakes further.
The timeline above shows some of the key events since 2017.