GENEVA: The US accused China Friday of conducting a secret nuclear test in 2020 as it called for a new arms control treaty that would bring in China as well as Russia. The accusations at a global disarmament conference highlighted serious tensions between Washington and Beijing at a pivotal moment in nuclear arms control, a day after the treaty limiting US and Russian missile and warhead deployments expired.The 2010 New START treaty which ran out Thursday left Russia and the US for the first time since 1972 without any binding constraints on their deployments of strategic missiles and warheads. President Trump wants to replace it with a new pact including China, which is rapidly increasing its own arsenal. In the meantime, Washington says it will keep modernising its own nuclear forces. “Russia and China should not expect the US to stand still while they shirk their obligations and expand their nuclear forces. We will maintain a robust, credible, and modernised nuclear deterrent,” US secretary of state Marco Rubio said.President Trump Thursday rejected an offer from President Putin to voluntarily extend the caps on strategic nuclear weapons deployments. On Friday, Russian and US negotiators discussed the expiration of the strategic arms pact, the Kremlin said. “There is an understanding, and they talked about it in Abu Dhabi, that both parties will take responsible positions and both parties realise the need to start talks as soon as possible,” Kremlin spokesman Dmitry Peskov said.Speaking at the disarmament conference in Geneva, US under secretary of state for arms control and international security, Thomas DiNanno said, “I can reveal that the US govt is aware that China has conducted nuclear tests, including preparing for tests with designated yields in the hundreds of tons.”China has used ‘decoupling’, a method to decrease the effectiveness of seismic monitoring, to hide their activities from the world,” DiNamo said. He said China had conducted one such “yield-producing test” on June 22, 2020.China’s ambassador on disarmament, Shen Jian said Beijing had always acted responsibly on nuclear issues. “China notes that the US continues to hype up the so-called China nuclear threat. China firmly opposes such false narratives,” he said. “It (the US) is the culprit for aggravating the arms race.”DiNanno said : “Today, the US faces threats from multiple powers. A treaty with only one nuclear power is inappropriate in 2026.” But Shen reiterated that his country would not participate in negotiations at this stage. “In this era we hope the US will abandon Cold War thinking and embrace cooperative security,” Shen said.