US President Donald Trump has condemned Iran as a "fanatical regime" and refused to continue certifying an international nuclear deal.
He said he was referring the deal to Congress and would consult allies on how to alter it.
He accused Iran of sponsoring terrorism and said he would deny the regime "all paths to a nuclear weapon".
International observers say Iran has been in full compliance with the 2015 deal freezing its nuclear programme.
But Mr Trump said the deal was too lenient, and Iran had been allowed to exceed heavy-water limits and intimidate international inspectors.
Iran, he said, was spreading "death, destruction and chaos".
It was "not living up to spirit of the deal", he said, but was receiving the benefit of sanctions relief regardless.
He said that the US reserved the right to leave the deal at any time.
Within minutes, EU's foreign policy chief Federica Mogherini insisted the deal was "robust" and that there had been "no violations of any of the commitments in the agreement".
She said it was not in the power of "any president in the world" to terminate the agreement, which had been established by a UN Security Council resolution.
Mr Trump had been under pressure at home and abroad not to scrap the seven-country deal.
He also focused on Iran's non-nuclear activities, particularly those of the Revolutionary Guards, which he called the "corrupt personal terror force of Iran's leader".
Credit:BBC News