In an interview with an Arab-based TV station, an influential foreign-affairs adviser to the Supreme Leader Ali Akbar Velayati said Washington should not dare carry out its military threats against Iran in an escalation of a war of words between Tehran and Washington.
"The Americans know very well that Iran and its allies in the region would retaliate very hard, that will make America face dark days to come," he said.
Last week, America imposed more sanctions on Iran after a missile test. Velayati added that Iran's foreign policy in the Middle East would not change and the US should just leave them alone as people in that region felt alienated by America's policies.
On US efforts to stop Iran from its missile program, Velayati described them as 'worthless fantasies.'
Since Trump took office, relations between the two countries have soured even more with Trump promising more stringent measures on Iran as he views it as having aggressive behavior towards America's allies in the region.
US National security adviser last week accused Iran of testing a missile capable of carrying a nuclear war head in contravention to a UN Security Council resolution. Iran confirmed testing the weapon, but said it did not contravene the UN resolution.
"Iran is playing with fire - they don't appreciate how 'kind' President Obama was to them. Not me!" The US President posted on Twitter after Iran ignored his warnings to refrain from testing the missile.