But critics in Congress want sanctions to remain in place, claiming that their harsh economic impact is what forced Iran to the negotiating table in the first place.
"The American people — Democrats and Republicans alike — overwhelmingly want Iran held accountable during any negotiations," Sen. Mark Kirk, R-Ill., said after Obama concluded his speech.
Obama also took credit for forcing the start of dismantling Syria's chemical weapons stockpile — a process he said was pushed by American diplomacy and threat of force.
The Obama administration had threatened to strike Syria's government, but backed down, after an Aug. 21 chemical weapons attack outside Damascus that the U.S. said killed more than 1,400 people. A month later, the U.N. Security Council approved a resolution to eliminate Syria's chemical weapons arsenal.
Obama promised anew to support opposition groups that are fighting to overthrow Syrian President Bashar Assad in that country's three-year civil war, and said the Syrian people deserve a future that is free of dictatorship, terror and fear.
Associated Press writer Josh Lederman contributed to this report.
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