Iran's stockpile of enriched uranium is more than five times the limit fixed under a landmark 2015 deal with world powers, the UN nuclear watchdog said Tuesday.
An International Atomic Energy Agency (IAEA) report said that as of February 19, 2020 the Iranian stockpile stood at 1,510 kilogrammes, as opposed to the 300 kg limit set under the agreement.
Some experts consider this level to provide sufficient material to produce a nuclear weapon.
However, it would still need several more steps, including further enrichment, to make it suitable for use in a weapon.
The report says that Iran has not been enriching uranium above 4.5 percent.
An enrichment level of around 90 percent would be needed for weapons use.
The latest IAEA report on the deal comes just days after a meeting in Vienna of the remaining parties to the deal which ended without a clear plan to keep the accord alive.
Rafael Grossi, the new head of the International Atomic Energy Agency (IAEA), who was in Paris to meet President Emmanuel Macron, told AFP: "Iran must decide to cooperate in a clearer manner with the agency to give the necessary clarifications."
"The fact that we found traces (of uranium) is very important. That means there is the possibility of nuclear activities and material that are not under international supervision and about which we know not the origin or the intent.
"That worries me," Grossi added.
The IAEA has for months been pressing Tehran for information about the kind of activities being carried out at the undeclared site where the uranium particles were found.
While the IAEA has not identified the site in question, diplomatic sources told AFP the agency asked Iran about a site in the Turquzabad district of Tehran, where Israel has alleged secret atomic activity in the past.
Iran began reneging on its commitments after the US pulled out of an agreement which offered sanctions relief in return.