"Beginning January 20, Iran will for the first time start eliminating its stockpile of higher levels of enriched uranium and dismantling some of the infrastructure that makes such enrichment possible," Obama said in a statement.
He said the move marked the first time in a decade that Iran agreed to take "specific actions" to halt progress and roll back key parts of its nuclear programme, by not installing or starting up additional centrifuges or using next-generation centrifuges.
Obama: Iran will start eliminating high levels of uranium
Under the interim deal reached with the six world powers in Geneva Nov 24, Iran agreed to curb parts of its nuclear activities for six months in exchange for eased sanctions, and pursue a comprehensive deal through negotiations with the US, Britain, France, Russia, China and Germany.
In a parallel deal with the International Atomic Energy Agency, the Islamic republic agreed to more frequent inspections of its nuclear sites by the nuclear watchdog.
"Taken together, these and other steps will advance our goal of preventing Iran from obtaining a nuclear weapon," said Obama.
"With today's agreement, we have made concrete progress. I welcome this important step forward, and we will now focus on the critical work of pursuing a comprehensive resolution that addresses our concerns over Iran's nuclear programme."
Noting the six powers and the European Union will start to ease sanctions on Iran, Obama said he "will veto any legislation enacting new sanctions during the negotiation" as "imposing additional sanctions now will only risk derailing our efforts to resolve this issue peacefully".
"I have no illusions about how hard it will be to achieve this objective, but for the sake of our national security and the peace and security of the world, now is the time to give diplomacy a chance to succeed," the U.S. president added.