Expert discusses Iran's nuclear capabilities before and after the US-Israeli attacks
NPR | By Leila Fadel
Published March 20, 2026 at 3:42 AM CDT
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LEILA FADEL, HOST:
For more on Iran's nuclear capabilities, I'm joined now by Ali Vaez. He's trained in nuclear physics. Most of us are not. He now directs the Iran project at the International Crisis Group, which is a think tank that works to prevent wars. Welcome back to the program.
ALI VAEZ: Good to be with you, Leila.
FADEL: So the reason why Trump chose to attack Iran keeps changing. It's regime change. It's long-range ballistic missiles. It's nuclear weapons. But I want to hone in on that one reason - that Iran was close to getting nuclear weapons. Was it? What is your assessment?
VAEZ: Iran was not close to getting nuclear weapons. But because President Trump withdrew from the nuclear deal with Iran in 2018, and that deal had basically put Iran's nuclear program in a box and under very rigorous monitoring, Iran was making very rapid advancements. And it was able to enrich enough uranium for a single nuclear weapon in a matter of few days, but it would still need an additional six to - six months to maybe a year to turn that into a deliverable nuclear weapon. And that was the assessment of the International Atomic Energy Agency as well as the U.S. intelligence community.
FADEL: What about the 12 days of bombing last summer on Iran by the U.S. and Israel? I mean, the president said at the time it had, quote, "completely obliterated" Iran's nuclear facilities. What's your assessment of Iran's nuclear capabilities then and now?
VAEZ: So in the run-up to that war, the amount of time that it would take Iran to enrich enough uranium for a single nuclear weapon was six days. And after that war, it was exactly the same amount of time. So - and this is because Iran had a stockpile of very advanced centrifuges that were in hidden underground clandestine facilities. And it also managed to maintain almost half a ton of 60% enriched uranium stockpiled, which, Leila, is just a little step away from weapons-grade. And that means that the two ingredients that Iran needed - the machines and the material - were already there before the 12-day war and also after the 12-day war, in addition to the fact that Iran has thousands of scientists and the know-how has already been acquired.
FADEL: Is there a clear assessment now of damage that's been done in this war on Iran's nuclear capabilities?
VAEZ: So the U.S. destroyed almost everything that was underground in the 12-day war. And in this war, it has also targeted some of the nuclear facilities, some of the bunker facilities. But at the end of the day, the key question really boils down to that stockpile of 60%, which is entombed in underground tunnels in Isfahan. We don't know if all of it is in the same place or dispersed in different tunnels, but that is really the shortest pathway that Iran has to nuclear weapons. And unless the president at the end of this war is able to address that particular question, he hasn't really resolved anything.
FADEL: Now, he hasn't fully ruled out ground troops. You know, he keeps the public guessing. But right now this is an air war. Is the - Iran's nuclear capability something that can be dealt with from the air?
VAEZ: At this point, it is not because there's nothing left really to bomb from the air. The U.S. can't eliminate all of Iran's nuclear scientific core and know-how. So without putting boots on the ground, either to retrieve that stockpile or to eliminate Iran's nuclear scientist, there is really no way that this could end. Now, putting boots on the ground is an extremely difficult mission because Isfahan is really in the middle of Iran. This is not an operation that you can do in a matter of a few hours, like the Osama bin Laden or even Maduro operation in Venezuela. You need to secure the environment. You need to have heavy machinery to be able to excavate this material. There might be some unexploded ordnances from the 12-day war. And these are massive 5,000-ton bombs that are there, so it's very difficult to neutralize them.
Then you get to nuclear material. If these cylinders have been broken and air and humidity has been mixed with uranium hexafluoride, it could kill you at first contact, so you have to have very specialized equipment. If you're not careful about how to move these cylinders out of that facility, you might actually start a nuclear chain reaction, a nuclear explosion. So this is an extremely difficult thing that would require maybe four, five days in the middle of a very hostile environment, which is very likely to result in massive American casualties.
FADEL: Let me ask you - I mean, 'cause from what you're saying, really, Iran's capabilities then and now, since the 12 days of bombing in the summer and this entire war, have not changed based on the strikes from the air. There's nothing left to bomb. What is the way, in your view, to actually deal with the stockpiles?
VAEZ: Well, there's - there was a diplomatic option on the table. Iranians were willing to dilute this material or to ship it out, obviously in return for sanctions relief. But President Trump chose not to pursue a diplomatic option and bombed the Iranian twice in the course of the last year in the middle of negotiations. So it's also, at this point, extremely difficult to imagine getting back to the negotiating table and finding a mutually acceptable solution. This is why this problem might have turned into one of those unsolvable situations, but Iran...
FADEL: Yeah.
VAEZ: ...Now actually having much more intent and higher motivation to develop nuclear weapons as the ultimate deterrent.
FADEL: So you're saying, actually, this might have the opposite effect of dealing with the nuclear capabilities - having the government of Iran actually pursue even harder?
VAEZ: Absolutely. I think at this point, the Iranians realize that the only thing that can protect them against future attacks are nuclear weapons. And the supreme leader who was killed in the opening act of this war had a religious edict against developing nuclear weapons, but that edict died with him. So at this moment, I don't see that there's any political or any other strategic obstacles in front of Iran for moving towards nuclear weapons.
FADEL: A lot of people can't help but think of Iraq - when the U.S. went to war then, claiming there were weapons of mass destruction. That turned out to be false. How reliable is the intelligence the U.S. has collected on Iran's nuclear capabilities?
VAEZ: I think it is very reliable because the U.S. intelligence never said Iran was on the verge of weaponization. They had always said Iran has the capability, but it hasn't made the political decision to cross the Rubicon and develop nuclear weapons. The U.S. intelligence never said that there was an imminent threat of Iran developing nuclear weapons. This was more a war of opportunity than a war of necessity.
FADEL: I also want to ask you about something that happened yesterday. Tulsi Gabbard testified in front of Congress. And in reading her prepared remarks, she skipped over a section where she was going to reference last summer and those attacks, saying that Iran's nuclear enrichment program was obliterated. What do you make of that decision?
VAEZ: Well, look. She's walking a very tight rope because I think she does understand that. The fact that the program was not fully obliterated, that Iran still has a pathway to nuclear weapon, are facts that the intelligence community is aware of. But saying that out loud might result in her falling from grace because the president would not accept that kind of assessment.
FADEL: Ali Vaez of the International Crisis Group. Thank you.
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