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 2015 deal has been hanging by a thread since the US withdrew from it in May 2018 and went on to impose stinging sanctions on Iran, in particular targeting its vital oil sector.

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.

The agreement promised Iran an easing of very damaging economic and other sanctions in return for its scaling back its nuclear programme.

Tehran has been progressively reducing its commitment to the accord however in retaliation for the US move.