GWEN IFILL: As U.S. critics of the nuclear agreement debate its merits, there is disagreement about whether it will achieve its intended goals elsewhere as well, including in Iran.

Jeffrey Brown has that story.

JEFFREY BROWN: While members of Congress debated the merits of the nuclear deal, there was also plenty of reaction in Iran itself, some pockets of celebration, some wariness about what it means and whether it's a positive outcome.

I spoke to New York Times Tehran bureau chief Thomas Erdbrink a short time ago.

Thomas Erdbrink, welcome.

Let's start in the streets, where the reaction from ordinary Iranians seems to have been somewhat muted?

THOMAS ERDBRINK, The New York Times: Well, a bit more muted than I expected, that's for sure.

I mean, you must consider the fact that these people have been living under these sanctions for years now, and a lot of people expected a massive street party, if you will, yesterday night when the news of the nuclear deal was announced. But it didn't happen.

There were several pockets of jubilation, if you will, across town, and a lot of people were out in their cars. But when you spoke to them, when you asked them, are you really happy, there were a lot of people with doubts. Some people said, maybe we have given up our nuclear plan too easily. Maybe we haven't negotiated enough.

Another says, you know what? Why have we suffered so much for 12 years, only for our leaders now to make a deal with the United States? So there was a mixed picture on the streets last night. People were confused and some were critical.

JEFFREY BROWN: There were even reports of police showing up to tamp down some of the celebrations that were happening.

THOMAS ERDBRINK: Well, I think, often in Iran, when you get a sort of semi-spontaneous gathering, some of the authorities get nervous.

And in the case of one of the squares where I was also president, people started shouting slogans in favor of the opposition leaders. Now, at that point, the police came out and sort of dispersed the people, only for them to later be allowed to again rejoin.

There wasn't a very tense situation. Actually, the atmosphere overall in the streets was very jubilant. People were honking their cars. They were happy, but, yes, there were also signs of criticism in the form of support for those opposition leaders that are under house arrest.

One of the election promises of Mr. — President Hassan Rouhani has actually been to get them freed, so people are reminding him of that fact as well.

JEFFREY BROWN: Now, just as President Obama faces a political fight over this, there are hard-liners in Iran against the deal. How much clout do they have and how might they go about trying to undercut it?

THOMAS ERDBRINK: Well, the picture is not as clear-cut as it is in the United States.

Iran's hard-liners, or conservatives, or however you want to label them, control several important power centers in the Islamic Republic, the state television, security forces, a large part of the economy. Now, these people have gone along with the deal because Iran's supreme leader, Ayatollah Khamenei, has sort of supported the negotiations.

And not only Iran's hard-liners, but basically everybody in this country is now waiting for what Supreme Leader Ayatollah Khamenei will say, and the first opportunity will be on Saturday, when he will speak before the nation marking the end of Ramadan. And a lot of the analysts expect him then to also give either his blessing for the nuclear deal or voice some critical points that he might have.

JEFFREY BROWN: So, you're saying it can't yet be considered a done deal from an Iranian perspective until he speaks?

THOMAS ERDBRINK: Technically, this deal is not signed by any of the parties.

Just as Congress will have a say in sort of agreeing or opposing this deal, in Iran, the Parliament will also have a say, in effect, whether this is a good deal or not. So, this is an on-site deal. It's called an agreement, a plan of action. So it's not the end of the story, as Iran's foreign minister said.

JEFFREY BROWN: Finally, is there a sense, an expectation among people that lifting sanctions could have a real impact in the lives of ordinary citizens or even perhaps lead to some political change there?

THOMAS ERDBRINK: For now, this news is sinking in very slowly. Iranians have been living through this roller coaster of negotiations for the past 22 months.

They have gone through deadline after deadline. And, by now, a lot of people are telling me, we have to see it to believe it first. And if you ask me about political change, that might be the hope by many in the West, that this deal will bring some form of Westernization of Iran. But if you listen closely to Iran's leaders, and you will conclude that they will not allow Starbucks and McDonald's to open up here in the wake of a broader Western change.

JEFFREY BROWN: Thomas Erdbrink of The New York Times, thanks so much.

THOMAS ERDBRINK: Thanks for having me.