US President Donald Trump says the United States will pursue additional sanctions that are "tougher than ever before" on Iran.
Opening a UN Security Council session, the President launched another broadside against Iran accusing it of proliferating items that could be used for weapons of mass destruction.
Mr Trump said: "The regime is the world leading sponsor of terror and fuels conflict across the region and far beyond."
He warned that Iran should "never be allowed" to be in possession of nuclear weapons.
"A regime with this track record must never be allowed to possess a nuclear weapon."
The US President insisted harsher sanctions would be in full force by November.
But the idea that sanctions would be enough to contain any biological or nuclear threats was met with scepticism by French President Emmanuel Macron.
Mr Macron said at the UN Security Council session on Wednesday that he thinks they need a "long-term strategy to deal with this crisis" he added that it was down to all members of the UN not just France, Germany and the UK.
On Tuesday, Theresa May met with Iran’s President Hassan Rouhani, to call for the release of the British charity worker, Nazanin Zeghari Ratcliffe.
The mother of one was detained at an airport in Tehran three years ago.
President Rouhani is said to have taken Theresa May’s ‘serious concerns’ on board - after Mrs May reiterated Britain’s commitment to the Iran nuclear deal.
This promise was repeated on Wednesday.