Iran advances research on uranium metal production
The latest move, which adds to pressure on US President-Elect Joe Biden just days before his inauguration, concerns Iran's plans to conduct research on uranium metal production at a facility in the city of Isfahan.
The Vienna-based International Atomic Energy Agency (IAEA) said in a statement that "Iran informed the Agency in a letter on 13 January that 'modification and installation of the relevant equipment for the mentioned R&D activities have been already started'".
Iran says the research is aimed at providing advanced fuel for a research reactor in Tehran.
"Natural uranium will be used to produce uranium metal in the first stage," the Iranian ambassador to the UN in Vienna Kazem Gharib Abadi said in a tweet.
The topic is sensitive because uranium metal can be used as a component in nuclear weapons and the 2015 deal contained a 15-year ban on "producing or acquiring plutonium or uranium metals or their alloys".
After 10 years Iran would have been allowed to initiate research on producing uranium metal-based fuel "in small agreed quantities" but only if the other parties to the deal had given approval.
In 2018 US President Donald Trump dramatically withdrew from the deal and went on to re-impose crippling economic sanctions on Iran.
The following year Tehran announced it would start breaking the deal's limits on its nuclear activity.
The breaches have included exceeding the stockpile limit on enriched uranium, enriching beyond the permitted purity level, and using more advanced centrifuges than permitted under the deal.
Tensions have increased since the assassination in late November of Iranian nuclear physicist Mohsen Fakhrizadeh.
In the aftermath of the attack, blamed on Israel, hardliners in Tehran pledged a response and Iran's parliament passed a controversial law calling for expanded nuclear activity and for an end to IAEA inspections.
The law also demanded Iran's Atomic Energy Organization "operate a facility of metal uranium production" within five months.
Iran says all of its breaches of the 2015 deal's limits are reversible, but insists that the US has to come back to the deal and lift sanctions first.
Biden has signalled he is willing to rejoin the pact but faces a tight window of opportunity between his own inauguration and presidential elections in Iran in June.