Washington, Jul 23: US President Donald Trump has warned Iran of grave consequences which a few countries have paid before, his national security advisor said today, hours after a stunning presidential tweet threatening Tehran.

"I spoke to the President over the last several days, and President Trump told me that if Iran does anything at all to the negative, they will pay a price like few countries have ever paid before," US National Security Advisor John Bolton said in a statement.

Bolton was responding to reporters' questions about Trump's tweet in which the president issued an unprecedented warning to Iran. In the nearly all-caps tweet, Trump mentioned about the dangers to Iran of making hostile threats after Iranian President Hassan Rouhani said, "America must understand well that peace with Iran is the mother of all peace and war with Iran is the mother of all wars."

"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!"Trump tweeted.

The White House today blamed Rouhani for inciting a war of words with President Trump, saying his tweet shows he is not going to tolerate critical rhetoric from Iran.

"If anybody's inciting anything, look no further than to Iran," White House press secretary Sarah Sanders said, adding President Trump has been "very clear about what he's not going to allow to take place."

Trump's tweet came hours after Secretary of State Mike Pompeo slammed Iran for its alleged human rights violation and destabilising activities in the region.

"Despite the regime's clear record of aggression, America and other countries have spent years straining to identify a political moderate. It's like an Iranian unicorn," Pompeo said in his major policy speech at the Ronald Regan Presidential Foundation and Library in Simi Valley, California on Sunday.

"We are asking every nation, every nation who is sick and tired of the Islamic Republic's destructive behaviour, to join our pressure campaign. This especially goes for our allies in the Middle East and Europe, people who have themselves been terrorised by violent regime's activity for decades," he said.

The United States is not afraid to spread its message on the airwaves and online inside of Iran either, he said. Responding to a question, Pompeo said Trump has been absolutely unequivocal on this not only in the message but in the fact that this is a real priority for the administration as well.

"I think that's important. One could have an objective, but if one doesn't rank it sufficiently high attention spans are short and resources limited. The President has put this as something he considers to be incredibly important," he said.

"The mission set for our team is clear. It's to deny the Iranian leadership the resources, the wealth, the funds, the capacity to continue to foment terrorism around the world and to deny the people inside of Iran the freedoms that they so richly deserve," he added.