WASHINGTON, Jan. 12 -- U.S. President Barack Obama on Sunday welcomed an agreement to start implementing an interim deal on Iran's nuclear program from Jan. 20, vowing to veto any legislation imposing new sanctions on the Islamic republic hereafter.

"Beginning January 20th, 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," the president said in a statement.

The move marks the first time in a decade that Iran has agreed to take "specific actions" to halt progress and roll back key parts of its nuclear program, by not installing or starting up additional centrifuges or using next-generation centrifuges, Obama said.

Under the interim deal reached with the six world powers in Geneva on 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 United States, Britain, France, Russia, China and Germany.

In a parallel deal with the International Atomic Energy Agency, the 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, adding "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 program."

The Obama administration has been trying to stop Congress from taking additional sanctions on Iran in the coming months, as some lawmakers are pushing hard for new legislation to rev up the pressure.

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.