- NEW: The White House says new sanctions would be "counterproductive"
- Iran to limit its nuclear program in exchange for sanctions relief starting January 20
- Talks will continue on a broader deal to prevent Iran from developing nuclear weapons
- A bipartisan proposal in Congress calls for imposing new conditional sanctions on Iran
Washington (CNN) -- The clock is ticking on an interim nuclear deal with Iran, as well as efforts in Congress to pass new sanctions for greater leverage in global negotiations on a comprehensive accord.
Sunday's announcement that a six-month interim agreement formally begins on January 20 means that Iran must dismantle or freeze some of its nuclear program and open it to more international inspections in return for limited relief from crippling international sanctions.
Assuming all goes as planned, further negotiations between Iran and the United States, France, Russia, China, Great Britain and Germany will seek a broader agreement intended to prevent Tehran from developing a nuclear weapon.
Meanwhile, pro-Israel members of Congress are seeking additional sanctions against Iran that would take effect if the talks break down.
The question is whether the steps Iran is taking under the interim deal will blunt or bolster the congressional push for more sanctions.
President Barack Obama warns that approving new sanctions legislation now would undermine the talks, and he promised Sunday to veto such a measure if it came to his desk.
"Our point is passing new sanctions now is counterproductive," White House spokesman Jay Carney told reporters on Monday.