GENEVA — A U.S. official focusing on arms control on Monday provided what he called new, declassified details of a Chinese underground nuclear test nearly six years ago and urged countries to press China and Russia to do more on nuclear disarmament. Christopher Yeaw, assistant secretary of state for the bureau of arms control and nonproliferation, spoke to a U.N.-backed body after the last nuclear arms pact between the United States and Russia expired this month. That has ended limits on the arsenals of the world’s biggest nuclear powers and raised concerns about a possible new arms race. READ: US says will match alleged […]... Keep on reading: US cites new details on China test, seeks disarmament push