Iran has announced it will raise its enrichment of uranium, breaking a deal designed to make it harder for the nation to create a nuclear weapon.
Iran will produce uranium at 5 per cent enrichment, above the limit of 3.67 per cent, government spokesman Ali Rabiei said.
The announcement is in contradiction to their 2015 promise to other world powers, and is likely to exacerbate further tensions with the US.
It comes less than a week after Iran admitted to breaking the deals 300kg limit on its low-enriched uranium stockpile.
Uranium can be used as fuel for nuclear power planes, but can also be developed into nuclear weapons.
The materials would need to be enriched to a level of 90 per cent to be made into a viable bomb.
Experts warn higher enrichment and a growing stockpile narrow the one-year window Iran would need to have enough material for an atomic bomb, something Iran denies it wants.
Iran made the decision a year after President Donald Trump unilaterally withdrew from the deal and imposed strict sanctions which have had a knock-on effect on the Iranian economy.
Since the sanctions were imposed, exports of crude oil have dropped from about 2.5 million barrels a day to around 300,000.
In a last-minute diplomatic bid, French President Emmanuel Macron spoke to his Iranian counterpart, Hassan Rouhani, by phone on Saturday, saying he is trying to find a way to resume dialogue between Iran and Western partners by July 15.