The Iran nuclear deal marks another milestone in Barack Obama's presidential tenure. Washington Post opinion columnist Jonathan Capehart explains how deeply this affects his legacy. (Jhaan Elker/The Washington Post)

President Obama’s defense of the complex and painstakingly negotiated nuclear deal that his administration reached with Iran boiled down to a simple, if controversial, contention: The only real alternative to the deal was war.

Obama returned to that conclusion repeatedly Wednesday at a news conference that stretched for more than one hour.

“Without a deal,” he said in his opening statement, “we risk even more war in the Middle East.”

A few minutes later, in response to a reporter’s question, Obama dismissed concerns that the House and Senate might vote down the deal, forcing him to use his presidential veto. Wouldn’t a rejection of the deal by lawmakers make him question its wisdom?

“Either the issue of Iran obtaining a nuclear weapon is resolved diplomatically through a negotiation or it’s resolved through force, through war,” Obama countered. “Those are — those are the options.”

Iran has finally reached a nuclear deal with the U.S. and international partners. Here's what's in the deal, and what happens next. (Gillian Brockell and Julio C. Negron/The Washington Post)

What about those who argued that Obama should have employed more diplomatic, economic or military leverage to get a “better deal” from the intransigent Iranians?

“What does that mean?” Obama asked rhetorically. “If the alternative is that we should bring Iran to heel through military force, then those critics should say so. And that will be an honest debate.”

The president’s news conference in the White House’s East Room came a day after his negotiators concluded contentious marathon talks with Iran. The deal they reached to limit Iran’s nuclear enrichment program — more than six years in the making — was swiftly condemned by virtually every major Republican presidential candidate.

A spokesman for House Speaker John A. Boehner (R-Ohio) said Wednesday that Obama, in defending the deal, had shown himself to be “hopelessly disconnected from reality.” Israeli Prime Minister Benjamin Netanyahu, addressing his country’s parliament a few hours before Obama spoke, left open the possibility of military action against Iran.

“We will reserve our right to defend ourselves against all of our enemies,” Netanyahu said. “We have strength, and it is great and mighty.”

The president responded with a defense of the nuclear agreement that was equal parts pugilistic and legalistic. Obama was briefed on the progress of the negotiations with Iran as often as twice a day and had amassed a detailed knowledge of the 109-page agreement and the additional 47 pages of annexes. He drew on that knowledge the way an experienced courtroom lawyer might rely on case-law expertise to answer criticisms that the deal didn’t last long enough; that it wouldn’t prevent the Iranians from covertly producing a nuclear weapon; that it still allowed the Iranians some nuclear enrichment capacity and therefore didn’t go far enough. He seemed eager to address every question.

“Have we exhausted [all the] Iran questions here?” Obama said at one point. “I am really enjoying this Iran debate. . . . Go ahead. Go ahead.”

President Obama took questions on the deal with Iran in the East Room of the White House on July 15. Here are key moments from that speech. (AP)

A few minutes later, Obama picked up a piece of paper from the lectern in front of him, eager to keep talking about the deal. “Okay,” he said. “I made some notes about many of the arguments — the other arguments that I’ve heard here.”

Obama’s defense of the deal wasn’t designed to win over dug-in critics, whom he dismissed as illogical and unrealistic. His audience was an American public worried about the threat posed by a nuclear-armed Iran but also exhausted by more than 14 years of war in Iraq and Afghanistan.

Obama has speculated in recent weeks that the nuclear deal could empower moderates in Iran who are eager for better relations with the rest of the world. “What I’d say to them is this offers a historic opportunity,” he told the New York Times in an interview Tuesday.

Such hopeful talk was largely absent Wednesday from Obama’s news conference, which focused on the dangers posed by Iran and the need to prevent the country from acquiring a nuclear weapon. “This has been a Democratic priority, this has been a Republican priority, this has been Prime ­Minister Netanyahu’s priority,” Obama said.

Obama hit on almost all the major criticisms of the deal during the news conference.

Republicans have criticized the deal for allowing Iran as many as 24 days before it grants inspectors access to military sites that could house covert programs. The delay could give Iran enough time to conceal illegal activity, critics said. Obama dismissed the charges as unrealistic and not grounded in science.

“This is not something you hide in a closet,” Obama said of the centrifuges and other sensitive equipment needed to make weapons-grade uranium. “This is not something you put on a dolly and kind of wheel off somewhere.”

Even if the Iranians had moved nuclear material from the site, Obama said, inspectors would find it. “Your high school physics will remind us that leaves a trace,” he said. “And so we’ll know, in fact, there was a violation of the agreement.”

Other critics have charged that the deal would pave Iran’s path to a bomb by lifting some of the most onerous restrictions on its nuclear energy program after 10 years.

“That’s a good one,” Obama said.

He countered that the inspections would still be in place 20 years from now. So, too, would Iran’s Non-Proliferation Treaty commitments. Iran would be about one year away from developing enough fuel for a nuclear bomb — a longer time frame than its current two to three months.

Yet another worry is that the lifting of tough economic sanctions on Iran would provide it with as much as $150 billion in revenue. Some of that money would be spent on infrastructure and the Iranian people. Some of it, critics say, would go to the likes of Hezbollah, Syrian President Bashar al-Assad and Iraqi militias that not long ago were killing Americans.

Here Obama suggested that the deal was better than any alternative. If negotiations broke down, Obama said, the United States would maintain tough sanctions but many of its partners, eager to do business with Iran, would drop them.

“So maybe they don’t get $100 billion,” Obama said of the Iranians. “Maybe they get $60 billion or $70 billion instead. The price for that . . . is that now Iran is pursuing a nuclear weapon” without any inspectors on the ground.

Obama seemed to be on less-certain ground when asked about his broader vision for the Middle East, which is going through a wrenching period of bloodshed, state collapse and militant attacks. He said that before he leaves office he wants to make sure that the United States is on track to defeat the Islamic State in Iraq. “We’re moving in the right direction there,” he said.

He talked about jump-starting a process to resolve Syria’s “open sore” of a civil war, but didn’t mention that the United States — despite months of work and millions of dollars — had managed to train only 60 moderate resistance fighters in that conflict.

He concluded by acknowledging that there were limits to his power.

“Ultimately, it’s not the job of the president of the United States to solve every problem in the Middle East,” Obama said. “The people in the Middle East are going to have to solve some of these problems themselves.”