AUDIE CORNISH, HOST:

In Saudi Arabia yesterday and in Israel today, President Trump bashed Iran. He often spoke during his campaign about his objections to Iran's deal with world powers to curb its nuclear programs. In a Saudi speech Sunday, the president called the country the world's biggest sponsor of terrorism. Here's part of what he said today.

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PRESIDENT DONALD TRUMP: The United States and Israel can declare with one voice that Iran must never be allowed to possess a nuclear weapon - never, ever - and must cease its deadly funding, training and equipping of terrorists and militias.

CORNISH: A reminder that these comments are coming at the same time that Iran just re-elected its moderate leader, President Hassan Rouhani. And for his part, President Rouhani called Trump's visit to Saudi Arabia a theatrical gathering and told the Associated Press today that relations with the U.S. are, quote, "a curvy road."

Now, to dig in on what this moment could mean for the U.S. and Iran, we're joined by Vali Nasr. He's dean of the Johns Hopkins School of Advanced International Studies. Welcome to the program.

VALI NASR: Thank you.

CORNISH: So we heard that phrase, a curvy road. We also saw President Rouhani telling the AP that he hopes the Trump administration will settle down. At the same time, President Trump has threatened to renegotiate the deal, the nuclear deal with Iran. But he hasn't done that. The U.S. has re-upped parts of the sanctions relief program for Iran. How does Trump's rhetoric match the reality of the administration's policy?

NASR: Well, so far, the administration has not actually ripped up the deal, but it is threatening to put additional sanctions on Iran for other sets of issues which in effect will negates whatever economic benefits Iran was going to get out of the deal. And then Rouhani in particular was hopeful that the nuclear deal would only be the first step in that curvy road that he described towards other deals and gradual opening of Iran. So even Trump's notion that the deal is not going to go anywhere from where it is - that's also not really welcome news to Rouhani and those who voted for him.

CORNISH: You know, President Trump has been saying on this trip that Israel and Arab nations have common cause in the threat posed by Iran. What's your take in how the president is trying to present these alliances here?

NASR: Well, he has gone back essentially to the Bush era where there was a really close United States-Arab alliance against Iran. But the picture has become quite complicated. For instance, in Iraq, the United States and Iran since 2003 have been backing the same Shia government. In the past year, the two have been fighting the same ISIS enemy. And without Iranian support for the campaign against ISIS, the current U.S. strategy in Iraq would not work.

So the president - I think President Trump jumped feet-first into a policy that is very popular in Riyadh and in other Arab capitals but actually does not address the complexity of interest that the United States has in different theaters of conflict in the region.

CORNISH: In the end, do you see the same irony that some analysts are talking about in the idea of Rouhani, comparative moderate, retaining power in Iran at the same time that you have an American president who is at least in speech looking for a harder line?

NASR: Yes, it is actually ironic, but also, it's even more ironic in that Rouhani - when he was elected first in Iran, he was a moderate. He moved significantly more to the left in order to get re-elected. And this is really a vindication of President Obama's initiative to carry out the nuclear deal, that the nuclear deal is now playing a transformative role in Iran's politics. And it's really a shame for the United States not to reap the benefit of a deal that it helped realize and let this moment in Iran pass without the United States taking advantage of it.

CORNISH: Vali Nasr - he's dean of the Johns Hopkins School of Advanced International Studies. Thank you for speaking with us.

NASR: Thank you. Transcript provided by NPR, Copyright NPR.