US President Donald Trump and Iranian President Hassan Rouhani have traded hostile warnings, amid rising tensions between the two countries.
Mr Trump tweeted that Iran "will suffer consequences the likes of which few throughout history have ever suffered before" if it threatened the US.
Mr Rouhani earlier said that war with Iran would be "the mother of all wars".
In May, the US left a deal which curbed Iran's nuclear activities in return for the lifting of international sanctions.
To Iranian President Rouhani: NEVER, EVER THREATEN THE UNITED STATES AGAIN OR YOU WILL SUFFER CONSEQUENCES THE LIKES OF WHICH FEW THROUGHOUT HISTORY HAVE EVER SUFFERED BEFORE. WE ARE NO LONGER A COUNTRY THAT WILL STAND FOR YOUR DEMENTED WORDS OF VIOLENCE & DEATH. BE CAUTIOUS!