JUDY WOODRUFF: We take a closer look at Iran's role in Yemen and its nuclear negotiations with the U.S.

Joining me is Thomas Erdbrink, The New York times' Tehran bureau chief, some of whose video reports we've aired on the NewsHour. He's in New York this week.

Thomas Erdbrink, thank you for joining us.

We have heard the Iranians deny they're supplying the Houthis with weapons, but we know the U.S. says that they are doing that, they have been doing that. We know the U.S. warships in the area are watching Iran ships to make sure they don't continue that. Why doesn't Iran just acknowledge what it's doing?

THOMAS ERDBRINK, The New York Times: Well, I think the Iranians, throughout the past decade, have been very covert about the way they have been supporting groups in either Afghanistan or Iraq.

And they apply the same policy in Yemen. I also think we shouldn't exaggerate the level of this military assistance. On one hand, you have the Saudis, who are leading a coalition of 10 countries who are attacking Yemen with warplanes. And the Iranians are potentially sending weapons, but I don't think we should expect that these weapons are of the highest standard or quality, not because the Iranians don't have them, but just they're — as you said yourself, there's so much scrutiny, it's hard for them to physically bring these weapons to Yemen.

And then I have been in Yemen once. It is a country awash with weapons. So I also don't know how many weapons the Iranians would actually need to send.

JUDY WOODRUFF: How do the Iranians view the war in Yemen, and do they see this as a much bigger conflict between themselves than Saudi Arabia?

THOMAS ERDBRINK: Well, the Iranians have been in competition with the Saudis in the region for a very long time, basically from the time of the shah.

But, recently, you know, following the withdrawal of the United States from the region out of Iraq, partly of Afghanistan, Iran has been filling up this vacuum. And this, of course, has been scaring the Saudis, who first started with an engineering a drop in oil prices, something that also hits the U.S. economy, but at the same time hits the Iranian economy, which is already under sanctions.

Now, the Iranians feel that their support for the Houthis is legitimate. I mean, you can doubt it, but they are saying Houthis are fighting for freedom, they are fighting with leaders of a country that has basically been collapsing over the past years. So their fight is a legitimate fight. And again they are pointing at what they call the double standards.

They're saying, look, the Saudis are attacking this country with airplanes, causing a lot of civilian victims, and our support is not that bad.

JUDY WOODRUFF: Well, let me turn you now to the nuclear issue. We know the talks resumed today in Vienna between Iran and other world powers over what's going to happen with Iran's nuclear program.

We heard an Iranian official say — repeating what the ayatollah said the other day, and that is that they expect sanctions, economic sanctions, to be lifted as soon as this agreement is completed. The U.S. and others are saying, no, it's going to happen in stages. What do the Iranians really expect in that regard and what about the Iranian people, the Iranian public? What are they looking for?

THOMAS ERDBRINK: Well, just to start with that last group, the Iranian public, ordinary people, they are waiting for the sanctions to be lifted yesterday, of course, so they want the sanctions to be lifted.

If you look at Iran's leaders, Iran's supreme leader, Ayatollah Ali Khamenei, the man who calls the shots in Iran, he has been arguing that on the first day of the signing of this agreement, all sanctions must be lifted.

Now, the foreign minister and the other officials, the people who are actually at the negotiating table, they are taking a different approach. They're saying the sanctions must be lifted on the day this agreement is implemented.

Now, there might be months, possibly a year between the signing of the agreement and the implementation of the agreement. So that gives, in my sense, enough wiggle space for all parties to come up with a reasonable compromise.

JUDY WOODRUFF: Very quick last question about The Washington Post reporter Jason Rezaian, who has been in jail for nine months in Iran. We have heard just this week the Iranians leveled — say they have imposed — or have leveled four charges, serious charges against him, including espionage.

What is expected will happen with this case?

THOMAS ERDBRINK: Well, let me first state that Jason Rezaian, first and foremost, is a friend of mine and my successor at The Washington Post, where I worked four years before I got to — went to The New York Times.

And these charges that have been leveled against him must be proven in a court of law. And according to Iranian law, the charges had to come way sooner than this. The court case needs to come very soon. I spoke to Jason's brother the other day. He also is expecting a court case. And this has taken very long.

If the Iranians are so convinced that Jason Rezaian is a spy, something I have never seen from him, then, OK, let them prove it in a court of law.

JUDY WOODRUFF: Well, we are — there is so much to keep an eye on.

And, Thomas Erdbrink, we thank you for talking to us while you're in New York. We appreciate it.

THOMAS ERDBRINK: Thanks for having me.