It would almost inevitably be followed by tit-for-tat reciprocal announcements by other nuclear-armed states, particularly Russia and China, and cement an accelerating arms race that puts us all in great jeopardy. It would also create profound risks of radioactive fallout globally. Even if such nuclear tests are conducted underground, this poses a risk interms of the possible release and venting of radioactive materials, as well as the potential leakage into groundwater.