Iran’s nuclear chief warned the United States on Monday of a “firm and strong reaction” if it persists in actions he says are endangering a nuclear deal aimed at curbing programs that Tehran could use to make atomic arms.

Ali Akbar Salehi was alluding to a bill before President Barack Obama that would extend U.S. sanctions under the Iran Sanctions Act l by 10 years. The bill was submitted to Obama after the U.S. Senate voted to extend it last week.

The nuclear deal between Iran and the United States and five other world powers lifted international sanctions in exchange for limitations on the Iranian nuclear program. But U.S. sanctions remain and will expire on Dec. 31 if Obama doesn’t sign the extension into law.

Speaking at a nuclear security conference convened by the U.N’s International Atomic Energy Agency, Salehi urged Washington to desist from “irrational and provocative” moves.

U.S. Secretary of Energy Ernest Moniz, who was also at the conference, said Salehi also “raised Iran’s concerns” during a meeting between the two men. He told reporters while Iran “strongly” views the Senate’s vote to extend the sanctions act as a violation of the nuclear deal, “I stated equally strongly that we do not view it” as such.

(AP)