A U.S. attack on a key Iranian nuclear facility might not be effective, even if American military’s massive bunker-buster bombs are used, a national security expert familiar with Iran’s program told ABC News on Thursday.
While the 30,000-pound bombs have been tested, they’ve never actually been used and the exact nature of the concrete and metal protecting the site located deep inside a mountain — that the bombs would need to penetrate — isn’t fully known.
Joe Cirincione, who has spent decades researching nuclear proliferation for Congress and other world leaders, told ABC News that while attacking Iran’s nuclear enrichment program would cripple its nuclear weapons capability, it would not eliminate it.
Airmen look at a GBU-57, or the Massive Ordnance Penetrator bomb, at Whiteman Air Base in Missouri, May 2, 2023.
U.S. Air Force via AP, FILE
At the center of President Donald Trump’s decision on whether to attack Iran is the Fordo nuclear enrichment facility in northwest Iran. It’s said to be built 300 feet deep inside a mountain — maybe more — and reinforced with concrete, according to experts.
The U.S. weapon touted as able to strike inside the Fordo facility the GBU-57 A/B Massive Ordnance Penetrator bomb, known as a “bunker buster.” It’s capable of penetrating 200 feet deep inside an underground target and then exploding, experts say.
A B-2 Spirit returns to Whiteman Air Force Base, Missouri, from a deployment to Diego Garcia, British Indian Ocean Territory, May 9, 2025.
Senior Airman Devan Halstead/509th Bomb Wing/US Air Force
Cirincione said that using the untested weapon would not guarantee success.
“Fordo is not an easy target. They made this very difficult for the United States to destroy,” he said. “Even [the bunker buster] can not penetrate 300 feet of mountain and reinforced concrete.
“You need to drop a bomb, that will dig a crater, and then another bomb in that crater and then another bomb, and then another,” he said. “And then you will only damage that part of the facility.”
Cirincione also noted that even if there’s some damage done, Iran’s government has the knowledge, experience and, most important, enough enriched uranium and centrifuges in other locationsto move forward with relative ease.
“You can’t bomb that,” he told ABC News. “You can slow it down, but they can pick up and start again fast and they know it.”
The International Atomic Energy Agency this week passed a resolution that stated Iran had breached its non-proliferation agreements and has been illegally stockpiling enriched uranium.
“I’ve been there, it’s half a mile underground,” Rafael Grossi, the IAEA’s director general, said about the Fordo plant, as reported by The New York Times.
Days after the IAEA acted, Israeli forces attacked Iranian targets after Israeli Prime Minister Benjamin Netanyahu claimed the Iranian government could create a nuclear weapon “in a very short time.”
Iranian officials have dismissed claims by Israel that they are building a nuclear weapon.
White House spokeswoman Karoline Leavitt told reporters Thursday that the president would make a decision about attacking Iran “in two weeks.”
Israel’s Prime Minister Benjamin Netanyahu in Israel, June 13, 2025, President Donald Trump in Washington, June 18, 2025 and Iran’s Supreme Leader Ayatollah Ali Khamenei in Tehran, June 13, 2025.
AFP via Getty Images/EPA-EFE/Shutterstock
Cirincione stressed that continued military strikes would not be a good option for Israel or the U.S. if the goal is an Iran without nuclear weapons.
“Once you recognize there is no military solution to this problem, the military solutions can only be threats to Iran and the only answer is to get Iran to agree to roll back and end its capabilities,” he said.