Iran is capable of resuming high-level uranium enrichment operations in five days if there is a "violation" of the nuclear deal with world powers, the head of the country's Atomic Energy Organisation has said.
Tehran's first priority was preserving the deal "but not at any price", Ali Akbar Salehi was quoted as saying by the official Irna news agency on Tuesday.
It comes after Iranian president Hassan Rouhani said last week that Iran could abandon the deal in hours if the United States continued with its policies of "sanctions and coercion" against Tehran.
Mr Salehi said Mr Rouhani's warnings were not baseless but rather based on available data.
The Fordo underground nuclear facility in Iran had been stabilised under the nuclear deal — officially called the Joint Comprehensive Plan of Action (JCPOA) — in a way that meant operations to produce 20 per cent enriched uranium could resume there within five days, he said.
Uranium that has been enriched to 20 per cent purity or higher is considered highly enriched, according to the International Atomic Energy Agency. Uranium needs to be enriched to 90 per cent purity to make an atom bomb.
"Preserving the Fordo facility is a point of strength of the (nuclear) deal," Mr Salehi added.
Following the nuclear deal, Iran — which says its nuclear programme is for peaceful purposes — drastically reduced the number of centrifuges installed at Fordo, and kept just over 1,000 there for research purposes. Centrifuges are the machines that enrich uranium.
The JCPOA states that no enrichment is permitted at the facility for 15 years.
The US treasury imposed sanctions on six Iranian firms in late July for their role in the development of a ballistic missile programme after Tehran launched a rocket capable of putting a satellite into orbit.
Earlier this month, US president Donald Trump also signed a senate bill that imposed sanctions on Iran, Russia, and North Korea.
Iran says the new US sanctions breach the JCPOA but Washington says they are unrelated to the deal.
* Additional reporting by Reuters