JERUSALEM (AP) — Iran and the United Nations’ nuclear watchdog are still negotiating over how to implement a deal struck last year to expand inspections of the Islamic Republic’s rapidly advancing atomic program, officials said Tuesday.

The acknowledgment by the International Atomic Energy Agency’s leader Rafael Mariano Grossi shows the challenges his inspectors face, years after the collapse of Tehran’s nuclear deal with world powers and the wider tensions gripping the Mideast over the ongoing Israel-Hamas war.

Grossi has already warned that Tehran has enough uranium enriched to near-weapons-grade levels to make “several” nuclear bombs if it chose to do so. He has acknowledged the agency cannot guarantee that none of Iran’s centrifuges may have been peeled away for clandestine enrichment.

“What we are looking at is concrete measures that could make this operational,” Grossi said.