The statement, by department spokesman John Kirby, was a departure from past US characterizations of the controversial site, which has been shut off to international nuclear inspectors since 2006.
The United Nations' International Atomic Energy Agency suspects Iran used the site in the past to experiment with nuclear weapons technology.Any site that hosts such activity
— whether it be military or civilian, declared or undeclared by a member state of the Nuclear Non-Proliferation Treaty to the IAEA—
Counts as a nuclear site in the eyes of the UN nuclear watchdog. That includes sites that host experimentation with fissile material, as well as those that do not, but instead experiment with nuclear weapons technology such as trigger mechanisms.
"It’s important to remember that when you’re talking about a site like Parchin, you’re talking about a conventional military site, not a nuclear site," Kirby said on Thursday. "So there wouldn’t be any IAEA or other restrictions on new construction at that site were they to occur."
Kirby was responding to reports of construction activity at the Parchin site.
Based on satellite imagery, the IAEA believes Iran is adding an additional facility to the complex.Tehran says it does not need the IAEA's permission to build or adapt military facilities.