JOHN YANG: Good evening.

I'm John Yang.

Iran# is bracing for global sanctions over its## nuclear program to go back in place.

The measures# threaten to cripple Iran's economy.

Their currency## is at a record low and ordinary Iranians are# struggling to get the food they need to survive.

The U.N.

Security Council rejected a# last ditch effort to delay the sanctions## after negotiations with European# nations failed to reach a deal.

Barring some sort of last# minute diplomatic breakthrough,## the renewed sanctions will freeze Iranian# assets abroad, penalize any development## of Iran's ballistic missile program, and ban# the sale or transfer of conventional weapons.

Frontline correspondent Sebastian Walker# conducted an exclusive interview earlier## this week with Ali Larijani, head of# Iran's Supreme National Security Council.

Seb, he previewed for you Iran's reaction# to these sanctions going back in place.## Let's listen to what he had to say.

ALI LARIJANI, Head of Iran's# Supreme National Security Council:## The issue of the snapback mechanism must be# ad.. SEBASTIAN WALKER, PBS Frontline# Correspondent: It's conditional.

ALI LARIJANI: Well when they stand against# us like so, and try to enforce resolution## against us using might, we see no reason to not# pursue a different relationships with the IAEA.

JOHN YANG: Tell us more.

Who is Ali# Larijani and why is this so significant?

SEBASTIAN WALKER: So he is the secretary of# Iran's Supreme National Security Council.

Now,## this is the body that essentially has the say over# foreign policy decisions, head of the security## apparatus and also strategy over the nuclear# program.

So essentially he's the chief negotiator.

What he says is extremely significant.

This# is a very rare conversation.

This is the first## time that he has spoken to foreign media since# his appointment.

It's also the first interview## that he's given since the 12-day conflict with# the U.S.

and Israel.

And the timing of this,## just in the lead up to everything that# we've heard at the U.N.

and this deadline## for the sanctions to come back, made this# a very interesting conversation to have.

JOHN YANG: You also asked him to react to the U.S.## claims that attack by the United States and# Israel obliterated their nuclear program.

SEBASTIAN WALKER: President Trump# has said that the enrichment## facilities targeted were completely# and totally obliterated.

Is he right?

ALI LARIJANI: You need to ask Trump himself, he# announced that his forces were brave and powerful,## that they bombed us and were successful.# You shouldn't discount his words.

SEBASTIAN WALKER:## What's your assessment of the extent to# .. how much this has set back Iran's nuclear program?

ALI LARIJANI: I don't have any specific# information to share.

But in my opinion,## Iran's nuclear program can never be destroyed.# Because once you have discovered a technology,## that can't take the discovery away.

It's# as if you are the investor of some machine,## and the machine is stolen from you.

Well, you have the knowledge# needed to make another one.

JONH YANG:## What was your takeaway.. SEBASTIAN WALKER: Well, this is obviously# at the heart of what's going on with this## question over whether U.N.

inspectors# should be allowed back in or not.## Iran wants to preserve as much mystery as they# can about the extent of the damage.

This is what## everyone wants to know.

Did these strikes succeed# in degrading Iran's enrichment facilities?

Were## the U.S.

strikes on Natanz, Fordow, Esfahan# sufficient enough to set back the program?

We asked for access to these facilities.

We# were pushing as hard as we possibly could on## the ground to get any filming done of any of# the strikes where the U.S.

missiles hit.

That## was -- we were told that was impossible.

And# you heard from Mr.

Larijani there that they## don't think that the bombed sites should be# open to U.N.

inspectors.

This is something## that he said really is conditional on# the sanctions not being reimposed.

He was saying essentially if these sanctions come# back, then they will end their participation with## the IAEA.

And you're seeing signs of that already.# Iran has recalled its ambassadors from Germany,## France, the U.K.

for consultations.

He# warned about the consequences of these## actions and that Iran could withdraw# from these negotiations as a result.

So, I mean, that was -- we pushed him# on, you know, a number of questions that## I think international observers have about# the impact of these attacks.

We asked him,## where is Iran's stockpile# of highly enriched uranium,## more than 400 kilos of HEU that Iran says is# buried under rubble.

International observers## want to know where that is.

And we asked him for# information about that.

None was forthcoming.

So, again, the takeaway overall is that# Iran really is trying to kind of preserve## whatever mystery it can about the extent# of the damage.

That's one of the few tools## that they really have left after this# devastating war that's taken place.

JOHN YANG: And you also asked him about# the possibility of more U.S.

attacks.

SEBASTIAN WALKER: What's your message# to the Trump administration if there## are more attacks?

What will# be the consequences of that?

ALI LARIJANI: I don't have a message for the# Trump administration.

I would only say that## they should be mindful of their words and# the insulting way they speak to Iranians.## When he says Iran must surrender., it's clear# he's not familiar with the Iranian people.

JOHN YANG:## Do you get the sense that they'r.. more attacks either from the# United States or from Israel?

SEBASTIAN WALKER: I think there's definitely# a worry about that.

The attacks, I mean,## were able to travel around the country to# places that were targeted.

We didn't see## the U.S.

strike sites, but were able to visit# locations where Israel had eliminated some## of Iran's leading nuclear scientists, places in# Tehran that had been bombed apartment buildings.

There's a real apprehension on# the part of Iranians that we met## that more strikes could be coming down the road.# There was, you know, alarm about how much had## happened during this war.

The 12-day conflict# really showed Iran's weaknesses to a lot of## ordinary people, that these scientists# could be eliminated so effectively.

And I think spending time in the country# while weren't able to really have a kind## of truly authentic engagement with Iranians# that we met.

You're very highly monitored,## controlled everywhere you go.

It's very# challenging as a reporter to report from Iran,## but there is a sense that these strikes# have really kind of had a huge impact.

The Iranian currency is at a record low.# The news of the sanctions coming back,## I think is incredibly worrying for a lot of# ordinary Iranians.

And it's just something## that I think is we're really now at a point where# anything could happen next.

The sanctions coming## back in puts Iran into a place where the# engagement with the international community## is now unclear.

You heard from Mr.

Larijani# there saying that they are going to withdraw## from participation with the IAEA.# And I think that begs the question,## what are going to be the consequences of that?# What are the U.S.

And Israel going to do next?

JOHN YANG: Frontline correspondent# Sebastian Walker, thank you very## much.

Sebastian's exclusive# interview will be part of an## upcoming documentary for PBS's Frontline# in collaboration with the Washington Post.