The United States is prepared to resume nuclear testing, potentially ending a decades-long moratorium, in response to alleged covert nuclear tests by China and Russia. A senior U.S. arms control official stated Tuesday that the U.S. will not tolerate an "unsupportable disadvantage," referencing President Donald Trump's earlier remarks. This potential move comes as the New START treaty, the last bilateral nuclear disarmament agreement between the U.S. and Russia, expired in early February, heightening proliferation concerns. While not indicating a return to large-scale atmospheric tests of the 1950s, the U.S. views this as a response to the "standards" set by China and Russia, citing seismic data from June 2020 as evidence of a Chinese test. The U.S. has called for multilateral arms control negotiations including China, and the decision on when to conduct an actual test rests with President Trump.