The United States has been secretly engaged in an attempt at back channel diplomacy with North Korea for months despite the increasingly bellicose public rhetoric between Washington and Pyongyang.

In the latest round of escalating threats President Donald Trump said the US military was "locked and loaded" while Kim Jong-un, the North Korean leader, accused him of "driving the Korean peninsula to the brink of nuclear war". Other nations, including Russia and China, called for calm.

In a tweet issued from his golf course in New Jersey, Mr Trump said: "Military solutions are now fully in place, locked and loaded, should North Korea act unwisely. Hopefully Kim Jong-un will find another path!"