Iran has further increased its stockpile of uranium enriched to near weapons-grade levels, a confidential report by the UN nuclear watchdog said Saturday and called on Tehran to urgently change course and comply with the agency’s probe.

Iran has increased production of highly enriched uranium, according to the United Nations nuclear watchdog, as the nation conducts talks with the United States on a nuclear deal.

The U.N. atomic agency reports that Iran hasn’t cooperated with a nuclear probe, raising the prospect of a snapback of sanctions on Tehran.