The IAEA said in a report Tuesday that its monitoring tasks in Iran had been "seriously undermined" after Tehran suspended some of the UN agency's inspections of the country's nuclear activities.

In February Iran suspended some IAEA inspections in response to the United States' refusal to lift sanctions on Iran.

"Since 23 February 2021 the Agency's verification and monitoring activities have been seriously undermined as a result of Iran's decision to stop the implementation of its nuclear-related commitments" under the 2015 nuclear deal with world powers, the International Atomic Energy Agency said in its report.

Iran has boosted its stocks of uranium enriched above the percentage allowed in the 2015 deal, it added.

Under the deal, Iran was not meant to enrich uranium above 3.67 percent, well below the 90-percent threshold needed for use in a nuclear weapon.

In addition it was only meant to have a stockpile of 202.8 kilos in total, equivalent to 300 kilos in a particular compound form.

However, the report estimates that Iran now has 2,441.3 kilos.

Of that amount, 84.3 kilos are uranium enriched to 20 percent (up from 62.8 kilos when the IAEA last reported in May); as well as 10 kilos are enriched up to 60 percent (up from 2.4 kilos).

The latest report comes as diplomatic efforts to revive the 2015 deal remain stalled, with Iran warning talks may not resume for months.