Several experts have cautioned that Iran likely moved a stockpile of near weapons-grade highly enriched uranium out of the deeply buried Fordow site before the strikes and could be hiding it.

The new assessment contrasted with U.N. agency view that Iran could resume enriching uranium in a “matter of months.”

The Pentagon on Wednesday sharpened its assessment of Iran's nuclear program, declaring that Iran's ability to build a nuclear weapon following the U.S. strike on its nuclear facilities is "closer to two years" away.