Obama Calls Iran Deal 'Most Consequential Foreign Policy Debate' Since Iraq Vote

This post was updated at 2:46 p.m. ET

President Obama delivered a foreign policy speech today aimed at bolstering public support for the Iran nuclear deal. He also attempted to discredit criticism from those who claim the agreement was a mistake.

"I've had to make a lot of tough calls as president. But whether or not this deal is good for American security is not one of those calls," Obama said during his remarks at American University, located about 10 miles from Capitol Hill.

The speech, which lasted just under an hour, laid out some of the agreement's details, like allowing inspectors access to Iran's "entire nuclear supply chain." This includes uranium mines and places where centrifuges are produced.

"This deal is not just the best choice among alternatives," Obama said. "This is the strongest non-proliferation agreement ever negotiated."

Congressional Republicans are almost universally opposed to the deal. The Republican-led House of Representatives announced earlier in the week that they've secured enough votes to disapprove of the Iran deal. That vote will take place next month, when Congress returns from the summer recess.

In an attempt to counter what the White House sees as likely lines of attack against the Iran deal in the coming weeks, the president went on the offensive today, saying it's hard to imagine a worse approach than blocking the agreement.

"Congressional rejection of this deal leaves any U.S. administration that is absolutely committed to preventing Iran from getting a nuclear weapon with one option – another war in the Middle East," Obama said.

Because the Iran agreement is not a treaty, congressional approval is not needed. But a vote of disapproval could significantly hamper the president's ability to suspend U.S. sanctions against Iran.

Winning over skeptical Democrats in Congress will also be crucial. If Obama vetoes a vote of disapproval, he would then have to find enough Democratic support to sustain the veto.