"This is a message that if the United States Congress blows up the deal that prevents Iran from obtaining a nuclear weapon, they will have to deal with the grave consequences that ensue," Earnest told reporters.
Legislation currently under consideration in Congress would "blow up the deal," the spokesman charged.
He said the only reason President Barack Obama didn’t veto an extension of the Iran Sanctions Act on Wednesday is that the law comports with US commitments under the Iran nuclear deal.
Both the House of Representatives and the Senate approved a 10-year extension of the sanctions law, which affects Iranian development of ballistic missiles and other weapons.
In July 2015, Iran and the so-called P5+1 group – the United States, Russia, China, France and the United Kingdom plus Germany – signed an agreement to maintain the nonmilitary nature of Tehran’s nuclear program in exchange for sanctions relief.