US President Donald Trump says he will withdraw the US from an Obama-era nuclear agreement with Iran.
Calling it “decaying and rotten”, he said the deal was “an embarrassment” to him “as a citizen”.
Going against advice from European allies, he said he would reimpose economic sanctions that were waived when the deal was signed in 2015.
In response, Iran said it was preparing to restart uranium enrichment, key for making both nuclear energy and weapons.
Iran’s President Hassan Rouhani said: “The US has announced that it doesn’t respect its commitments.
“I have ordered the Atomic Energy Organisation of Iran to be ready to start the enrichment of uranium at industrial levels.”
He said he would “wait a few weeks” to speak to allies and the other signatories to the nuclear deal first.
“If we achieve the deal’s goals in cooperation with other members of the deal, it will remain in place,” he said.
The so-called Joint Comprehensive Plan of Action (JCPOA) curbed Iran’s nuclear activities in return for the lifting of sanctions that had been imposed by the UN, US and EU.
Mr Trump had previously complained that the deal only limited Iran’s nuclear activities for a fixed period; had failed to stop the development of ballistic missiles; and had handed Iran a $100bn (£74bn) windfall that it used “as a slush fund for weapons, terror, and oppression” across the Middle East.
Former President Barack Obama, who signed the deal on behalf of the US three years ago, called Mr Trump’s announcement “misguided”.
When will the sanctions restart?
The US Treasury said economic sanctions would not be reimposed on Iran immediately, but would be subject to 90-day and 180-day wind-down periods.
In a statement on its website, it said sanctions would be reimposed on the industries mentioned in the 2015 deal, including Iran’s oil sector, aircraft exports, precious metals trade, and Iranian government attempts to buy US dollar banknotes.
US National Security Advisor John Bolton is reported as saying that European companies doing business with Iran will have to finish within six months or face US sanctions.