US President Donald Trump threatened to obliterate parts of Iran if the Islamic Republic attacked "anything American", as Iran said the latest US sanctions had closed off any chance of diplomacy.
"Any attack by Iran on anything American will be met with great and overwhelming force," Mr Trump tweeted just days after the United States came within minutes of bombing Iranian targets.
"In some areas, overwhelming will mean obliteration," the US president tweeted.
Mr Trump yesterday signed an executive order imposing sanctions against Supreme Leader Ayatollah Ali Khamenei and other senior figures.
Sanctions against Foreign Minister Mohammad Javad Zarif are expected later this week.
"Imposing useless sanctions on Iran's Supreme Leader and the commander of Iran's diplomacy is the permanent closure of the path of diplomacy," Iranian Foreign Ministry spokesman Abbas Mousavi tweeted.
"Trump's desperate administration is destroying the established international mechanisms for maintaining world peace and security."
The moves came after Iran shot down a US drone last week and Mr Trump called off a retaliatory air strike minutes before impact.
It would have been the first time the United States had bombed Iran in decades of hostility between them.
Mr Trump said last week that he had decided at the last minute that too many people would die.
Iran leadership doesn't understand the words "nice" or "compassion," they never have. Sadly, the thing they do understand is Strength and Power, and the USA is by far the most powerful Military Force in the world, with 1.5 Trillion Dollars invested over the last two years alone..
— Donald J. Trump (@realDonaldTrump) June 25, 2019
....The wonderful Iranian people are suffering, and for no reason at all. Their leadership spends all of its money on Terror, and little on anything else. The U.S. has not forgotten Iran's use of IED’s & EFP’s (bombs), which killed 2000 Americans, and wounded many more...
— Donald J. Trump (@realDonaldTrump) June 25, 2019
....Iran's very ignorant and insulting statement, put out today, only shows that they do not understand reality. Any attack by Iran on anything American will be met with great and overwhelming force. In some areas, overwhelming will mean obliteration. No more John Kerry & Obama!
— Donald J. Trump (@realDonaldTrump) June 25, 2019
In a televised address today, Iranian President Hassan Rouhani said sanctions against Mr Khamenei would have no practical impact because the cleric had no assets abroad.
Mr Rouhani, a pragmatist who won two elections on promises to open Iran up to the world, described the US moves as desperate and called the White House "mentally retarded" - an insult that other Iranian officials have used in the past about Mr Trump, but a departure from Mr Rouhani's own comparatively measured tone.
Mr Rouhani and his cabinet run Iran's day-to-day affairs, while Mr Khamenei, in power since 1989, is Iran's ultimate authority.
"The White House actions mean it is mentally retarded," Mr Rouhani said. "Tehran's strategic patience does not mean we have fear."
US sanctions
The United States has imposed crippling economic sanctions against Iran since last year, when Mr Trump withdrew from an agreement between Tehran and world powers to curb Iran's nuclear programme in return for the lifting of sanctions.
The crisis has escalated sharply since last month, when the Trump administration tightened the sanctions, ordering all countries to halt purchases of Iranian oil.
That has effectively starved the Iranian economy of the main source of revenue it uses to import food for its 81 million people, and left Iran's pragmatic faction with no benefits to show for its nuclear agreement.
The US says the 2015 agreement reached under Mr Trump's predecessor Barack Obama did not go far enough because it is not permanent and does not cover issues beyond the nuclear programme, such as missiles and regional behaviour.
Iran says there is no point negotiating with the US when it has abandoned a deal that was already reached.
The downing of the US drone, which Iran says was over its airspace and the US says was in international skies, followed weeks of rising tension that had begun to take on a military dimension.
The United States and some regional allies have blamed Iran for attacks on tankers in the Gulf, which Tehran denies. Washington's European allies have repeatedly warned both sides of the danger that a small mistake could lead to war.
