"If fully implemented, this framework," he said, "will cut off every pathway Iran could take to develop a nuclear weapon." And "If Iran cheats, the world will know."
As Iran did not "come to the table in a serious way", Obama said the US had "rallied the world to impose the toughest sanctions in history, profoundly impacting Iran's economy."
"Sanctions couldn't stop Iran's nuclear programme on their own, but they helped bring Iran to the negotiating table," he said.
"And after many months of tough and principled diplomacy, the United States - joined by the United Kingdom, France, Germany, Russia, China, and the European Union - achieved the framework for a deal," Obama said. In return for Iran's actions, the international community has agreed to provide Iran with relief from US sanctions and international sanctions imposed by the UN Security Council, he said.
"This relief will be tied to the steps Iran takes to adhere to the deal. And if Iran violates the deal, sanctions can be snapped back into place," Obama said. According to a US factsheet issued after the talks, the outline deal also includes these conditions:
Iran will reduce its installed centrifuges - used to enrich uranium - by two-thirds and reduce its stockpile of low-enriched uranium. The centrifuges that are no longer in use will be placed in storage, monitored by the International Atomic Energy Agency.
All of Iran's nuclear facilities will be subject to regular IAEA inspections. Iran will redesign its heavy-water reactor in Arak so that it cannot produce. India, which is Iran's second-biggest buyer on an annual basis after China, has been gradually reducing its oil imports from Tehran under US pressure.