Iran will not let U.S. domestic politics thwart ongoing nuclear negotiations, an Iranian official said, moments after President Barack Obama said he will sign legislation that allows Congress to have the power to review any final deal. "That is an issue related to their domestic affairs. We are dealing with the American government," Iran Foreign Ministry spokeswoman Marzieh Afkham said at a news conference carried by state television. For at least the past month, Republicans and some Democrats have been urging Obama to approve legislative oversight of the nuclear negotiations. The development injects a new element of uncertainty into the final stages of diplomatic negotiations between major world powers and Iran, aimed at curbing Tehran's nuclear program in exchange for sanctions relief.