Obama says the agreement is the product of years of work between Iran and six world powers, not just between the U.S. and Iran. He says a diplomatic solution that keeps Iran from obtaining a nuclear weapon is preferable to an "unconstrained" Iranian nuclear program or another war in the Middle East.
President-elect Donald Trump, who takes office on Friday, vowed at times during the presidential campaign either to walk away from the deal or to renegotiate it.
Iran agreed in 2015 to limit its ability to enrich uranium in exchange for the removal of some international economic sanctions.
Read Obama's full statement below:
"Today marks the one-year anniversary of the implementation of the Joint Comprehensive Plan of Action (JCPOA) - a deal that has achieved significant, concrete results in making the United States and the world a safer place. This historic understanding reached between the United States, France, the United Kingdom, Germany, China, Russia, the European Union and Iran has rolled back the Iranian nuclear program and verifiably prevents Iran from obtaining a nuclear weapon.
One year ago, the International Atomic Energy Agency (IAEA) verified that Iran had fulfilled key commitments spelled out under the JCPOA. Instead of steadily expanding, Iran's nuclear program faces strict limitations and is subject to the most intrusive inspection and verification program ever negotiated to monitor a nuclear program. Iran reduced its uranium stockpile by 98 percent and removed two-thirds of its centrifuges. Meanwhile, Iran has not enriched any uranium at the Fordow facility nor used advanced centrifuges to enrich. In short, Iran is upholding its commitments, demonstrating the success of diplomacy.
While this deal was intended to address Iran's nuclear program, we have remained steadfast in opposing Iran's threats against Israel and our Gulf partners and its support for violent proxies in places like Syria and Yemen. We continue to be deeply concerned about U.S. citizens unjustly imprisoned in Iran. And our sanctions on Iran for its human rights abuses, its support for terrorist groups, and its ballistic missile program will remain until Iran pursues a new path on those issues. There is no question, however, that the challenges we face with Iran would be much worse if Iran were also on the threshold of building a nuclear weapon.
The United States must remember that this agreement was the result of years of work, and represents an agreement between the world's major powers - not simply the United States and Iran. Moreover, the Iran deal must be measured against the alternatives - a diplomatic resolution that prevents Iran from obtaining a nuclear weapon is far preferable to an unconstrained Iranian nuclear program or another war in the Middle East."