This would be in breach of Iran’s deal with six world powers – China, France, Germany, Russia, the US and the UK, signed in 2015.
Under the deal, Iran was only permitted to enrich uranium up to 3.67% purity.
The deal also saw Iran agree to operate no more than 5,060 of its oldest and least efficient IR-1 centrifuges and to cease enrichment at the underground Fordo facility.
The country also agreed to hold no more than 300kg (660lbs) of low-enriched uranium.
Highly enriched uranium, which has a purity of 20% or more, is typically used in research reactors.
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