The president argues that preventing Iran from having any enrichment capacity is simply impossible. The key, he insists, is how well you curb it and verify its limitations: “Now, Prime Minister Netanyahu would prefer, and many of the critics would prefer, that they don’t even have any nuclear capacity. But really, what that involves is eliminating the presence of knowledge inside of Iran. Nuclear technology is not that complicated today, and so the notion that the yardstick for success was now whether they ever had the capacity possibly to obtain nuclear weapons — that can’t be the yardstick. The question is, Do we have the kind of inspection regime and safeguards and international consensus whereby it’s not worth it for them to do it? We have accomplished that.”

The president said he knows he is going to have a fight on his hands with Mr. Netanyahu and those in Congress who share the prime minister’s views, but he seemed confident that in the end he would prevail.

Mr. Netanyahu, Mr. Obama said, “perhaps thinks he can further influence the congressional debate, and I’m confident we’re going to be able to uphold this deal and implement it without Congress preventing that. But after that’s done, if that’s what he thinks is appropriate, then I will sit down, as we have consistently throughout my administration, and then ask some very practical questions: How do we prevent Hezbollah from acquiring more sophisticated weapons? How do we build on the success of Iron Dome, which the United States worked with Israel to develop and has saved Israeli lives? In the same way I’m having conversation with the gulf countries about how do we have a more effective interdiction policy, how do we build more effective governance structures and military structures in Sunni areas that have essentially become a void that [the Islamic State] has filled or that, in some cases, Iranian activities can exploit?”

The president added: “And what I’ve also tried to explain to people, including Prime Minister Netenyahu, is that in the absence of a deal, our ability to sustain these sanctions was not in the cards. Keep in mind it’s not just Iran that paid a price for sanctions. China, Japan, South Korea, India — pretty much any oil importer around the world that had previously import arrangements from Iran — found themselves in a situation where this was costing them billions of dollars to sustain these sanctions.

“In some ways, the United States paid the lowest price for maintenance of sanctions, because we didn’t do business with Iran in the first place. They made a significant sacrifice. The reason they did was because my administration, our diplomats, and oftentimes me personally, were able to persuade them that the only way to resolve this nuclear problem was to make these sanctions bite. And if they saw us walking away from what technical experts believe is a legitimate mechanism to ensure that Iran does not have a nuclear weapon — if they saw that our diplomatic efforts were not sincere, or were trying to encompass not just the nuclear program, but every policy disagreement that we might have with Iran, then frankly, those sanctions would start falling apart very rapidly. And so, maybe Iran wouldn’t get $150 billion, but they’d get a big chunk of that, because we would not be able to sustain that support.”

It strikes me that the one party that we have heard the least from, but in the end could count the most, is the Iranian people and how they ultimately react to this opening of Iran to the world as a result of this deal. What would Mr. Obama say to them?

“What I’d say to them is this offers a historic opportunity,” the president said. “Their economy has been cratering as a consequence of the sanctions. They have the ability now to take some decisive steps to move toward a more constructive relationship with the world community. … They need to seize that opportunity, their leaders need to seize that opportunity. And the truth of the matter is that Iran will be and should be a regional power. They are a big country and a sophisticated country in the region. They don’t need to invite the hostility and the opposition of their neighbors by their behavior. It’s not necessary for them to be great to denigrate Israel or threaten Israel or engage in Holocaust denial or anti-Semitic activity. Now that’s what I would say to the Iranian people. Whether the Iranian people have sufficient influence to fundamentally shift how their leaders think about these issues, time will tell.”