"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!," Trump wrote in a Twitter post late on Sunday night.

'LONG-IGNORED VOICE OF PEOPLE'

Rouhani on Sunday said "war with Iran is the mother of all wars", but did not rule out peace between the two countries.

"We are no longer a country that will stand for your demented words of violence & death," Trump tweeted. "Be cautious!" he added.

US Secretary of State Mike Pompeo has also launched a rhetorical assault on Iran's leaders, comparing them to a "mafia" and promising unspecified backing for Iranians unhappy with their government.

Pompeo, in a California speech to a largely Iranian-American audience on Sunday, dismissed Rouhani and Foreign Minister Javad Zarif, who negotiated a nuclear deal with the United States and five other countries, as "merely polished front men for the ayatollahs' international con artistry."

US President Donald Trump withdrew in May from the 2015 nuclear accord designed to stop Iran from developing nuclear weapons. Tehran has said its nuclear work is just for electricity generation and other peaceful projects.

Iran "is run by something that resembles the mafia more than a government," Pompeo said, citing what he called Iranian leaders' vast wealth and corruption.

Pompeo's speech was the latest step in a communications offensive launched by the Trump administration that is meant to foment unrest in Iran and help pressure its government to end its nuclear program and support of militant groups, US officials familiar with the matter said.

Australian Associated Press