"Because of other countries testing programs, I have instructed the Department of War to start testing our Nuclear Weapons on an equal basis," he wrote on social media just before meeting with Chinese President Xi Jinping in South Korea. The US has more nuclear weapons than any other country, Trump said, with Russia second and China a "distant third". It has not conducted nuclear testing since 1992. It comes just days after Trump denounced Russia for testing a nuclear-powered missile. The Kremlin says its tests were "not nuclear".

Later, on Air Force One after the two leaders' meeting, Trump said the nuclear test sites would be determined later. "With others doing testing, I think it's appropriate that we do also," Trump said on his way back to Washington. No country except North Korea has conducted a nuclear test explosion in this century, according to the Arms Control Association (ACA) - and even Pyongyang announced a moratorium in 2018. Trump's announcement did not make it clear whether he was referring to testing a nuclear explosion, or simply a weapon system that would be capable of delivering a nuclear weapon. (BBC)