During Israel's latest attack on Iran at the end of In October, an active top-secret nuclear weapons research center was destroyed, reports "Axios".
It is about the "Taleghan" facility. 2 at the Parchin Military Complex, about 20 miles southeast of Tehran.
The attack reportedly damaged sophisticated equipment used to engineer the plastic explosives that surround the uranium in a nuclear device and are needed to detonate it.
A US official said on condition of anonymity that the facility was carrying out "scientific activity that could lay the foundation for the production of nuclear weapons".
The source also added that it was "top secret", even unknown to most of the Iranian government.
Iran is enriching uranium to 60 percent purity, close to the roughly 90 percent needed to make an atomic bomb. If this material were further enriched, it would be enough for two nuclear weapons, according to the IAEA.
Iran denies that it is trying to build nuclear weapons, but no other country has enriched uranium to this level unless it is aiming for such production.