Tensions between Washington and Tehran have deepened as US president Donald Trump warned that any attack by Iran on the United States could lead in part to its "obliteration".
“Any attack by Iran on anything American will be met with great and overwhelming force. In some areas, overwhelming will mean obliteration,” Mr Trump tweeted. “The USA is by far the most powerful military force in the world.”
Asked in the White House whether he had an exit strategy if war breaks out with Iran, Mr Trump replied "I don't need exit strategies". The US was ready for "whatever" Iran chose to do, he said.
....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
His comments came as Iranian president Hassan Rouhani, in a televised address, accused the US leadership of being "mentally retarded" – the first public reaction by Tehran to the Trump administration's decision to impose sanctions on senior Iranian figures on Monday.
Tensions have been high in the Gulf region in recent months as Iran has struggled under the impact of crippling economic sanctions and the US has increased its military presence in the region.
The two sides moved perilously close to military confrontation last week when Iranian forces shot down an unmanned US naval drone and the US made preparations for a military strike, which was cancelled at the last moment by Mr Trump.
In his address, Mr Rouhani also said sanctions against Ayatollah 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 used the term “mentally retarded” about the US leadership – 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 Ayatollah 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.”
The US 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 penalties.
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 Tehran uses to import food for its 81 million people, and left Iran’s pragmatic faction with no benefits to show for its nuclear agreement.
Washington 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 Washington when it has abandoned a deal that was already reached.
The downing of the US drone – which Iran says was over its air space and the US says was in international skies – followed weeks of rising tensions that had begun to take on a military dimension.
The US 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.
Meanwhile the White House announced that Stephanie Grisham, currently a senior aide to Melania Trump, will replace Sarah Huckabee Sanders as White House press secretary. Mr Trump said Ms Grisham would do "a great job". – additional reporting: Reuters