JUDY WOODRUFF: From Lausanne, Switzerland, today, news of a nuclear deal. The United States and five other nations say they have achieved a political framework for a final agreement with Iran.

After more than a year-and-a-half of negotiations, two blown deadlines, and all-nighters this week, it came down to an afternoon of announcements, starting with the E.U. foreign policy chief, Federica Mogherini.

FEDERICA MOGHERINI, Foreign Policy Chief, European Union: We gather here to find solutions towards a reaching comprehensive resolution that will ensure the exclusively peaceful nature of the Iranian nuclear program and the comprehensive lifting of all sanctions. Today, we have taken a decisive step.

JUDY WOODRUFF: Among the main points of the deal announced today: Iran's uranium enrichment capacity will be limited for 15 years, and the number of centrifuges it operates for that purpose will be reduced from 19,000 to 6,100. Enrichment will be allowed to continue only at the Natanz nuclear facility.

At the Arak facility, the reactor creating weapons-grade plutonium will be redesigned to halt that activity. In return, and after verification, United Nations, European Union and U.S. sanctions will be lifted.

That sets the stage for Iran and six world powers, the U.S., France, Germany, United Kingdom, China and Russia, to negotiate the text of a final accord.

MOHAMMAD JAVAD ZARIF, Foreign Minister, Iran: We have stopped a cycle that was not in the interest of anybody.

JUDY WOODRUFF: Iran's foreign minister, Javad Zarif, called it a win-win, showing Iran is dedicated to peace without giving up its right to nuclear activity.

MOHAMMAD JAVAD ZARIF: None of those measures include closing any of our facilities. The proud people of Iran will never accept that. Our facilities will continue. We will continue enriching. We will continue research and development. Our heavy water reactor will be modernized.

JUDY WOODRUFF: At the same time, he noted the fragile state of newly reopened U.S.-Iran diplomacy.

MOHAMMAD JAVAD ZARIF: But we have serious differences with the United States. We have built mutual mistrust in the past. So, what I hope is that, through courageous implementation of this, some of that mistrust could be remedied, but that is for us all to wait and see.

JUDY WOODRUFF: And back in Washington:

PRESIDENT BARACK OBAMA: It is a good deal, a deal that meets our core objectives.

JUDY WOODRUFF: President Obama offered his own assessment and an updated take on President Reagan's attitude on dealing with the Soviets: Trust, but verify.

PRESIDENT BARACK OBAMA: So this deal is not based on trust, it's based on unprecedented verification. If Iran cheats, the world will know it. With this deal, Iran will face more inspections than any other country in the world.

JUDY WOODRUFF: Mr. Obama directly addressed one of the fiercest critics of a deal with Iran, Israeli Prime Minister Netanyahu. He said he would be speaking with him and with other concerned allies in the region.

PRESIDENT BARACK OBAMA: So when you hear the inevitable critics of the deal sound off, ask them a simple question: Do you really think that this verifiable deal, if fully implemented, backed by the world's major powers, is a worse option than the risk of another war in the Middle East?

JUDY WOODRUFF: And the president pleaded with members of Congress, some of whom have voiced strong opposition to the administration's course.

PRESIDENT BARACK OBAMA: If Congress kills this deal — not based on expert analysis, and without offering any reasonable alternative — then it's the United States that will be blamed for the failure of diplomacy. International unity will collapse, and the path to conflict will widen.

JUDY WOODRUFF: The nuclear negotiators will now focus on technical aspects of the Iran program, facing a hard deadline of June 30.

U.N. Secretary-General Ban Ki-Moon congratulated negotiators on today's agreement, and said a comprehensive deal in a few months could — quote — “enable all countries to cooperate urgently” to deal with many security challenges they face.

Meanwhile, House Speaker John Boehner criticized today's announcement, calling it — quote — “an alarming departure from President Obama's initial goals.”

Joining us now tonight again tonight, under very different circumstances, is Indira Lakshmanan of Bloomberg News in Lausanne, Switzerland.

So, Indira, they have announced the deal. What is the U.S. side saying? Are they saying they got what they wanted?

INDIRA LAKSHMANAN, Bloomberg: They are. And, in fact, I think they're saying that they are surprised in end that they got as much as they wanted, insofar as we heard from some administration officials who were involved in the negotiation afterward that there were moments in these very difficult negotiations, as recently as yesterday and today, where they said to the Iranians, look, maybe you're just not going to be able to agree to this. Maybe it isn't going to work.

In the end, if you look at this four-major, very detailed fact sheet that the White House put out, it looks like on the surface at least as if the United States has gotten everything that it has been asking for and demanding for the last year. Now, of course, the proof is going to be in the pudding, which is in the next three months, these negotiations could still potentially fall apart over the very difficult parts of the how to get those things accomplished, the actual technical steps that each side is going to have to take.

And that's not guaranteed yet. And Secretary Kerry made that clear, that it could still fall through. But I have to say that, on the face of it, even though some aspects are still left vague, the administration appears to be coming home to Washington with pretty much, as I said, everything it had thought and that it had hoped it would get in the last year.

JUDY WOODRUFF: Well, they know they are facing a skeptical Congress, though, with a Republican majority who is already raising criticisms about this. They're not betraying any concerns about that?

INDIRA LAKSHMANAN: Well, they admit that they know they are going to have an uphill battle with Congress.

And there are a lot of skeptics in Congress who are going to try to poke holes in this. We have already heard people saying today that some of the flaws, that the snap-back function of the sanctions is not clear yet, how they are going to establish the possible military dimensions of Iran's past work, and also how the U.N. sanctions are going to be lifted.

So, some things were mentioned as goals they want to do, but it was not clear how they are going to get there. On the other hand, even some of the most fierce critics of the Obama administration on the nuclear side came out today saying that, actually, this was a much better deal than they had expected and that it was the kind of thing that they thought would be a good deal, if in fact tough implementation measures were put in.

And one thing Secretary Kerry said again and again is that this deal has no sunset clause. That's interesting. So, on the verification, some last for 10 years, some for 15, some for 25, looking at the entire life of uranium in Iran.

That's a huge thing. And other aspects of it will never end, was the point he was making. So I think they have some strong arguments to bring back home, even though they are definitely going to face people who are dead-set against any deal with Iran because they simply don't trust anything that the Ayatollah Khamenei would agree to.

JUDY WOODRUFF: Indira Lakshmanan of Bloomberg News, we thank you.