Iran and six world powers will begin implementing an interim agreement designed to pause parts of Iran's nuclear program.
The White House said that beginning Jan. 20, Iran will begin eliminating its stockpile of "higher levels of enriched uranium and dismantling some of the infrastructure that makes such enrichment possible."
In return the the five permanent members of the United Nations — the U.S., Russia, China, the U.K. and France — plus Germany will ease some sanctions on Iran.
"With today's agreement, we have made concrete progress," President Obama said in a statement. "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. 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."
Obama also said that he would veto any legislation that implements new sanctions on Iran.
As we reported back in November, Iran and the world powers reached a six-month deal in the hopes that during that time the two sides could reach a permanent deal.
All of this, of course, has to do with the West's belief that Iran is working toward making a nuclear weapon. The West wants Iran to be more transparent about its program and to stop enriching uranium. Iran has always maintained that its program is peaceful and that it has the right to enrich uranium.
In a statement, Secretary of State John Kerry said: "While implementation is an important step, the next phase poses a far greater challenge: negotiating a comprehensive agreement that resolves outstanding concerns about the peaceful nature of Iran's nuclear program."
Kerry said the U.S. is "clear-eyed" about the challenges facing the negotiations.
"These negotiations will be very difficult, but they represent the best chance we have to resolve this critical national security issue peacefully, and durably," Kerry said.
Update at 1:44 p.m. ET. The Change In Iran:
Of course, one of the reasons the international community has gotten to this point is Iran's new President Hassan Rouhani, who has proven to be a lot more moderate than his predecessor, Mahmoud Ahmadinejad.
On Saturday, All Things Considered host Arun Rath talked to Scott Peterson of the Christian Science Monitor, one of the few Western journalists in Iran.
Peterson said Rouhani's election has changed things in the country.
"Many people told me after the election and the violence of 2009, they told me they would never cast a ballot again, that they couldn't trust that their vote would be counted or anything like that," Peterson said. "So one of the dynamics that has yielded this kind of resurgence of hope or re-engagement of Iranians and their political future and in the politics of today is the fact that they themselves overcame their doubts about the election system and basically went out to vote and elect by a very thin majority, this more moderate cleric as president."
Peterson notes, however, that the more conservative faction of Iran is suspicious of Rouhani and especially suspicious of any deal with the United States.