FILE PHOTO: An Iranian flag flutters in front of the International Atomic Energy Agency (IAEA) headquarters in Vienna, Austria…
FILE - Caption FILE PHOTO: An Iranian flag flutters in front of the International Atomic Energy Agency (IAEA) headquarters in Vienna, Austria, Sept. 9, 2019.

The UN's atomic watchdog says Iran has nearly tripled its stockpile of enriched uranium over the past three months, in sharp violation of the 2015 nuclear deal it signed with six world powers.

The International Atomic Energy Agency (IAEA) also said on Tuesday that Iran appears to have three undeclared atomic sites. The IAEA said it is insisting on “clarifications” from Tehran.

Iran in 2015 signed the nuclear accord with the five permanent members of the UN Security Council plus Germany and the European Union. The United States abandoned the deal in 2018 and introduced new sanctions against Iranian officials and can punish entities that do business with Tehran.

Iran has said it no longer considers itself bound by the agreement and has gradually reduced some of its commitments under the deal.

It has said it would be willing to move back to full compliance with the deal if Europe provides “meaningful” economic benefits, but it has complained that Germany, France, and Britain have not done enough to mitigate the harm U.S. sanctions have caused.

In its report, the IAEA said Iran’s stockpile of low-enriched uranium had reached 1,020.9 kilograms, far above the limit of 300 kilograms allowed in the agreement.

In its previous report, in November 2019, the IAEA said the stockpile was at 372.3 kilograms.

Some experts have said Iran is reaching a level sufficient to produce a nuclear weapon, but they caution it would require several more steps — including further enrichment — to make the material suitable for use in a bomb.

Iran has insisted that its nuclear program is strictly for civilian and energy uses.

The IAEA also said that Tehran refused to grant access to two of three suspected nuclear sites that the UN agency wanted to visit in late January.

"The agency identified a number of questions related to possible undeclared nuclear material and nuclear-related activities," it said.

IAEA chief Rafael Grossi, told AFP that "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," Grossi said.

"That worries me," he added.