The U.S. military’s unprecedented strikes on Iran’s nuclear facilities last month set back the country’s nuclear program by one to two years, according to top Defense Department spokesman Sean Parnell.

Parnell maintained during Wednesday’s Pentagon briefing that the U.S. strikes resulted in the “total obliteration of Iran’s nuclear ambitions,” which has been the Pentagon’s stance on the strikes since they occurred, though he added, “We have degraded their program by one to two years at least.”

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“I think we’re thinking probably closer to two years, like degraded their program by two years,” he said. He added that when factoring the totality of the strikes from a “psychological” perspective, “We believe that Iran’s nuclear capability has been severely degraded, perhaps even their ambition to build a bomb.”

His comments on how far the United States set back Iran’s nuclear program marked the first detailed assessment from the Pentagon.

A preliminary analysis from the Defense Intelligence Agency that was leaked to the media after the strikes suggested, with low confidence, that Iran’s nuclear program had only been delayed by months. The leak of the report prompted an FBI investigation.

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Defense Secretary Pete Hegseth and President Donald Trump disagreed with the assessment’s conclusions and argued the strikes had a devastating effect.

The U.S. targeted three of Iran’s facilities: Fordow, Natanz, and Isfahan. The Fordow facility was considered the most impenetrable, given it was built under a mountain. The U.S. had to deploy its most powerful nonnuclear bomb, which it had never used before in battle, to target it.

The U.S. began planning the operation targeting the Fordow facility about 15 years ago.

The head of the International Atomic Energy Agency, Rafael Grossi, said last week the damage to Iran’s nuclear program was “severe” but not “total,” and he added that they could restart producing enriched uranium “in a matter of months.”

Following the U.S. attack on Iran’s nuclear facilities, Iran carried out what was largely a symbolic retaliatory attack on the U.S.’s Al Udeid Air Base in Qatar.