Iran has dragged its feet on providing access to three sites suspected of past possible involvement in Iran’s nuclear program, the director general of the International Atomic Energy Agency (IAEA) said in a new report today. If not resolved, the development could eventually lead to Iran’s nuclear file being referred back to the UN Security Council, adding new pressure to already strained diplomatic efforts to try to bring Iran back into full compliance with the 2015 Iran nuclear deal.

A separate IAEA report issued today said that Iran has significantly increased its stockpile of low-enriched uranium, including, since November, at the underground Fordow facility, which is built into a mountain-side near Qom. Iran is now enriching uranium using 1,044 IR-1 centrifuges in the underground site, noted Daryl Kimball, executive director of the Arms Control Association.

Under the Joint Comprehensive Plan of Action (JCPOA), Iran stopped all enrichment at Fordow, for three years. But it restarted it in November as one of a series of steps the past year to protest the US reimposition of crippling sanctions on Iran’s banking and energy sectors after President Donald Trump quit the deal in 2018 and launched his maximum pressure campaign against Tehran.

“Iran has not provided access to the agency to two locations … and has not engaged in substantive discussions to clarify agency questions related to possible undeclared nuclear material and nuclear-related activities in Iran,” IAEA Director General Rafael Mariano Grossi wrote in a report on its safeguards agreement with Iran to the IAEA Board of Governors. “This is adversely affecting the agency’s ability to clarify and resolve the questions and thereby to provide credible assurance of the absence of undeclared nuclear material and activities in Iran.”