The White House says it would veto new congressional legislation that would toughen sanctions against Iran.

Senators from both parties introduced the legislation on Thursday. They did so despite appeals from the White House, which wants to avoid implementing new penalties while the U.S. is holding nuclear negotiations with the Islamic republic.

White House spokesman Jay Carney says the sanctions would undermine American diplomatic efforts.

The bill sets restrictions that would go into effect if Tehran violates an interim nuclear deal it reached with world powers last month or lets the agreement expire without a long-term accord. A Senate vote won’t happen until January at the earliest, and it’s unclear whether the bill will have enough support to pass.

(AP)