President Rouhani raised the threat of military conflict in an address to his country’s diplomats on Sunday, as reported by state agency IRNA.
He said: “Mr Trump, don’t play with the lion’s tail, this would only lead to regret.
“America should know that peace with Iran is the mother of all peace, and war with Iran is the mother of all wars.”
His heated message provoked a livid response from Mr Trump who wrote a searing retort, all in capitals, on Twitter last night.
Mr Trump said: 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!”
Why has Rouhani warned USA of ‘mother of ALL wars’?
The violent tirade follows months of worsening relations between the two nations, ignited by the US’s decision to leave a deal to lift international sanctions on Iran if it halted nuclear activities.
The US left the Iran Deal, known formally as the Joint Comprehensive Plan of Action (JCPOA), on May 8 after Mr Trump called it a “horrible, one-sided deal that should never, ever been made”.
The move was heavily criticised by the UK and other members of the United States Security Council, plus Mr Trump’s predecessor Barack Obama.
Tehran previously justified its work as necessary for generating electricity, among other peaceful projects.
Washington’s planned sanctions include shutting down imports of Iranian oil, currently one of the large exports for the country.
The US originally intended to force countries into buying any oil from Iran but has since softened its position.
Last month, India said it was preparing for a “drastic reduction or zero” imports of Iranian oil from November, according to industry sources.
Reuters said the agreement was being made despite India saying it followed UN sanctions rather than the ones imposed by the United States.
In a separate provocation on Sunday, US Secretary of State Mike Pompeo compared Iranian leaders to the “mafia”.
He told an Iranian-American audience in California the country “is run by something that resembles the mafia more than a government,” citing what he called Iranian leaders’ vast wealth and corruption.
He added the US’s actions were not about “regime change” but about curbing Iran’s nuclear and missile work.
Mr Pompeo said: “While it is ultimately up to the Iranian people to determine the direction of their country, the United States … will support the long-ignored voice of the Iranian people.”