WASHINGTON – President Donald Trump insisted Wednesday that U.S. strikes delivered a crushing blow to Iran’s nuclear program despite a preliminary American intelligence assessment suggesting that the assault inflicted only a marginal setback.

“This was a devastating attack, and it knocked them for a loop,” Trump said as his administration deployed a phalanx of top officials to defend his claims that Iran’s nuclear program was “completely and fully obliterated.”

Defense Secretary Pete Hegseth said the leaked intelligence assessment, which said Iran suffered a delay of only a few months, was “preliminary” and “low confidence.” Secretary of State Marco Rubio said the officials who disclosed the findings are “professional stabbers.”

The White House pointed to a statement from the Israel Atomic Energy Commission that said Iran faced a setback of “many years.”

Drawing reliable conclusions about the impact of the U.S. strikes is difficult, making the issue a breeding ground for competing claims that could determine how American voters view Trump’s risky decision to join Israel’s attacks on Iran.

Also at stake are Trump’s next steps in the Middle East, where diplomatic efforts could be required to prevent Iran from rebuilding its nuclear program.

Iran maintains that its atomic ambitions are for peaceful purposes, while U.S. and Israeli leaders have described the country’s nuclear program as the precursor to obtaining a nuclear weapon.

One of the targets of the U.S. attack was Fordo, where nuclear infrastructure is buried deep underground. The Israeli commission said in a statement that the bombing “rendered the enrichment facility inoperable.”

The statement was distributed by the White House and the office of Israeli Prime Minister Benjamin Netanyahu.

“The American strikes on Iran’s nuclear facilities, combined with Israeli strikes on other parts of Iran’s military nuclear program, have “set back Iran’s ability to develop nuclear weapons by many years,” the statement said.

In addition, Iranian Foreign Ministry spokesman Esmail Baghaei told Al Jazeera that there was significant damage from U.S. bombers.

“Our nuclear installations have been badly damaged, that’s for sure,” he said.

The episode has triggered some of Trump’s longstanding vendettas against leaks and intelligence officials, who he has often viewed as a part of a “deep state” dedicated to undermining his agenda. He also lashed out at media outlets that reported on the classified assessment, describing them as “scum” and “disgusting.”

Trump said questioning the effectiveness of the strikes was disrespectful to the military, which flew stealth bombers halfway around the world to attack the nuclear facilities with weapons designed to penetrate deep underground.

The reports, he said, were “very unfair to the pilots, who risked their lives for our country.”

One critical question is whether enriched uranium, which could be developed into fuel for a nuclear bomb, was moved out of facilities before the U.S. strikes.

“I believe they didn’t have a chance to get anything out, because we acted fast,” Trump said. He added that “it’s very hard to move that kind of material, and very dangerous.”

Classified briefings for lawmakers, originally scheduled for Tuesday, are now expected to take place on Thursday and Friday.