North Korea has condemned the U.S. for conducting a no-explosion nuclear experiment that it claims destabilizes global security, vowing to recalibrate its own nuclear deterrence measures in response.

The U.S. Energy Department’s National Nuclear Security Administration (NNSA) announced last week that it conducted a “subcritical experiment at an underground facility in Nevada on May 14 to collect information about the reliability and effectiveness of American nuclear warheads.

“This is a dangerous act that renders the extremely worsening global security environment more unstable, having seriously negative impact on the strategic balance among major nuclear powers,” an unnamed spokesperson of North Korea’s