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Russia - which tested a new nuclear-powered cruise missile on October 21, held nuclear readiness drills on October 22 and tested a new nuclear-powered autonomous torpedo on October 28 - said it hoped Trump had been properly informed that Moscow had not tested a nuclear weapon itself.

"President Trump mentioned in his statement that other countries are engaged in testing nuclear weapons. Until now, we didn't know that anyone was testing," Kremlin spokesman Dmitry Peskov told reporters.

Putin, who commands the world's biggest arsenal of nuclear warheads, has repeatedly said that if any country tests a nuclear weapon then Russia will do so too.