evening, and to a major development on iran. President obama this sunday saying the u.S. And other countries will begin to give iran some relief from those economic sanctions with iran now agreeing to... See More
evening, and to a major development on iran. President obama this sunday saying the u.S. And other countries will begin to give iran some relief from those economic sanctions with iran now agreeing to start curbing their nuclear activities. You'll remember this image of the president last fall, talking on the phone with iran's new president. The first direct contact between an american president and an iranian lieader since 1979. I want to bring in our chief white house correspondent jonathan karl right now. Jon, when does iran have to begin implementing this deal? Actions speak louder than words. Reporter: David, january 20th is the day that iran will begin to scale back part of its program eliminating some of its nuclear fuel. And in exchange, they will get $7 billion in sanctions relief. The white house released a statement, saying this is the best chance to get an agreement that will finally put to end fears that iran is developing a nuclear bomb. Jon, some want new sanctions as an insurance policy? Reporter: A major movement right now in congress, led by a top democrat, to impose new sanctions on iran right now. The white house says that would derail this diplomatic effort. In fact, david, the president in that statement today issued a veto threat, saying if congress passes sanctions, he will veto them. Big fight ahead. Jon karl at the white house with us on a sunday night. Jon, thank you.
This transcript has been automatically generated and may not be 100% accurate.