US President Donald Trump has sent the Iranian President an aggressive warning via an all-caps tweet.
At about 11:30pm on Sunday (local time), Mr Trump posted a message to Twitter which was addressed to Hassan Rouhani.
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Writing in all capital letters, he chastised Iran for 'threatening' the US and demanded the country stop or "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," the former real estate tycoon wrote. "BE CAUTIOUS!"
The passionate tweet seems to be a response to President Rouhani's recent comments that Mr Trump "stop playing with the lion's tail".
"America must understand well that peace with Iran is the mother of all peace and war with Iran is the mother of all wars," he told a gathering of Iranian officials.
In turn, US Secretary of State Mike Pompeo compared Iran's leaders to a "mafia" in a speech on Sunday. He referred to President Rouhani and Foreign Minister Javad Zarif as "merely polished front men for the ayatollahs' international con artistry".
Since withdrawing the US from the Iran nuclear deal in May, the Trump administration has launched a full-scale assault on the country, reportedly with the goal of sowing civil unrest and pressuring the government to end both its nuclear programme and its support of militant groups.
The US government plans to reimpose sanctions on Tehran's oil exports in the coming months.