The Trump administration dropped some serious allegations Tuesday: China secretly detonated an underground nuclear weapon back in 2020, and they've got seismic data to back it up.

The Evidence Points to Lop Nur

Christopher Yeaw, who leads the State Department's Bureau of Arms Control and Nonproliferation, laid out the case at the Hudson Institute in Washington. The alleged test happened on June 22, 2020, near China's Lop Nur nuclear test site in Xinjiang, according to The Washington Post.

"We're not going to remain at an intolerable disadvantage," Yeaw declared.

Here's what caught their attention: seismic monitoring equipment in neighboring Kazakhstan picked up a magnitude 2.76 event. The problem? It didn't look like an earthquake or a mining explosion, which are the usual suspects for underground tremors in that region.

Yeaw suggested China employed "decoupling" techniques to dampen the blast and mask how powerful it actually was. Think of it as trying to muffle a firecracker so your neighbors don't hear it, except with nuclear weapons. "We know that they were preparing designated tests of hundreds of tons," he noted.

For context, the Comprehensive Nuclear-Test-Ban Treaty Organization did detect "two very small seismic events, 12 seconds apart" but said they were too small to determine what caused them. So we're in disputed territory here.

America Returns to Nuclear Testing

These accusations arrive alongside a major policy shift. Last year, President Trump ordered the Defense Department to restart full-scale nuclear weapons testing for the first time since 1992. That's a three-decade pause, broken.

Trump framed it as a necessary response to Russia and China's growing nuclear capabilities. He argued the US needed to test on equal footing with both countries, though he pointed out America already maintains the world's largest and most sophisticated nuclear stockpile, which was modernized during his first term.

The timing was notable: Trump announced the testing decision hours before meeting Chinese President Xi Jinping in South Korea. That was their first face-to-face since 2019, and Trump chose not to bring up nuclear testing during the actual meeting.

In defending the move, Trump emphasized that China's rapid nuclear expansion and North Korea's continued testing made it critical to verify US nuclear weapons still work as intended. He said America had become the only nation not conducting nuclear tests and he wasn't comfortable staying in that position.

Trump also mentioned he'd discussed denuclearization with both President Vladimir Putin and President Xi Jinping, though those conversations apparently didn't change his calculus on resuming US testing.