Iranian President Hassan Rouhani on Sunday cautioned U.S. President Donald Trump about pursuing hostile policies against Tehran, saying “war with Iran is the mother of all wars”, but did not rule out peace between the two countries.

Iran faces increased U.S. pressure and looming sanctions after Trump’s decision to withdraw the United States from a 2015 international deal over Iran’s nuclear programme.

Addressing a gathering of Iranian diplomats, Rouhani said: “Mr Trump, don’t play with the lion’s tail, this would only lead to regret,” the state news agency IRNA reported.

“America should know that peace with Iran is the mother of all peace, and war with Iran is the mother of all wars,” Rouhani said, leaving open the possibility of peace between the two countries, at odds since the 1979 Islamic Revolution.

“You are not in a position to incite the Iranian nation against Iran's security and interests,” Rouhani said, in an apparent reference to reported efforts by Washington to destabilise Iran’s Islamic government.

Reacting later on Sunday, Trump issued an all-caps threat to Iran. The tweet was sent at 11:24 p.m. after the president returned to the White House from spending the weekend at his golf club in Bedminster, New Jersey.

Trump wrote: “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!”

The comments came at the same time as Secretary of State Mike Pompeo was speaking at a Reagan Forum in Simi Valley, California, on the topic of Iran.

Pompeo blasted the country for corruption and human rights abuses – but also offered direct talks with the regime.

Ten minutes into his speech, he was heckled by a protester, who shouted about the Trump administration “kidnapping children.” The protester continued to shout, but she was drowned out by audience members shouting her down, and chants of “USA! USA!”

The chaotic scene lasted for 30 seconds or so, with Pompeo eventually quipping, “If there were only so much freedom of expression in Iran,” to cheers and applause.

•Pieced together from reports by Reuters and ABC News.