“The idea that it’s a big redesign doesn’t hold water,” said Hans M. Kristensen, director of the Nuclear Information Project at the Federation of American Scientists, a private research organization in Washington. “They’ve already tested the part that goes bang.”
Mr. Whiton, however, believes that even modest changes “ought to be proved in the real world.” He also argued that the United States would have to develop new warheads to counter an emerging class of superfast weapons — known as hypersonics — that China and Russia are developing. “It’s likely that new warhead designs will be necessary,” he said, and will require new testing.
Despite the conflicting claims and uncertain election outcomes, nuclear experts say that China and Russia are readying their test sites for new detonations, perhaps in case the United States restarts its program, or alternatively to race ahead on their own. Dr. Moniz, the former secretary of energy, said he fears that Washington will go first if Mr. Trump wins a second term.
Mr. Whiton, the former State Department adviser, cast doubt on the idea that a U.S. detonation would set off a global chain reaction. He noted that Russia and China were already building up their arsenals without recourse to new testing.
“It is unclear if existing and aspiring nuclear states would follow us,” he said of a global reaction. “If they do, the downside is that they might improve their capabilities marginally.”
