Iran’s Foreign Minister Javad Zarif fired back at United States President Donald Trump’s threats against Iranian President Hassan Rouhani, warning him to “be cautious”.

“COLOR US UNIMPRESSED,” Zarif tweeted, mimicking Trump’s tweet written in capital letters. “The world heard even harsher bluster a few months ago. And Iranians have heard them —albeit more civilized ones — for 40 yrs. We’ve been around for millennia [and] seen fall of empires, incl [including] our own, which lasted more than the life of some countries. BE CAUTIOUS!”

Zarif was responding to Trump’s tweet on Monday threatening Iran with “consequences the likes of which few throughout history have ever suffered before”. “Never, ever threaten the United States again,” the US president had tweeted in capital letters.

Trump’s tweet came a day after Iranian President Rouhani had warned him against inciting Tehran with hostile policies. Rouhani had said “war with Iran is the mother of all wars” in his address to Iranian diplomats.

Relations between the US and Iran have been tense since Trump announced in May his decision to pull Washington out of a nuclear agreement with Iran, calling it “decaying and rotten”. The US has said it will re-impose sanctions against Iran and has asked some other countries to take similar action.