Russia has stolen hypersonic cruise missile technology from the United States, U.S. President Donald Trump’s top national security aide John Bolton said while discussing last week’s deadly explosion at a military test site in Russia’s north. The mysterious explosion that killed five Russian nuclear engineers and caused a radiation spike last Thursday has spawned conflicting theories over its cause. Amid high secrecy and the absence of thorough explanations from Russian authorities, outside observers have concluded that the explosion occurred during testing of a nuclear-powered cruise missile.

Bolton on Russia's nuclear capability. @VOA Contributor @Greta Van Susteren interviews National Security Adviser John Bolton in which they discussed Russia's technological advances to develop their nuclear weapons. pic.twitter.com/Dm9fLE6uaN — The Voice of America (@VOANews) August 14, 2019

“Something obviously has gone badly wrong here,” Bolton told the U.S.-funded Voice of America (VOA) news outlet in an interview published early Thursday, referring to the Russian explosion. He called the accident in the White Sea “an example of Russia trying to make technological advances in their ability to deliver nuclear weapons.” “Although Russia’s economy is roughly the size of the Netherlands’, it’s still spending enough on defense to not only modernize their nuclear arsenal, [but] to build new kinds of delivery vehicles, hypersonic glide vehicles, hypersonic cruise missiles largely stolen from the American technology,” Bolton said.