As Chinese officials were flying to Washington for talks on the North Korean threat and other security issues, Donald Trump caught them and his own advisers off guard by declaring that China had failed in its efforts to convince Pyongyang to abandon its nuclear programme.

“While I greatly appreciate the efforts of President Xi & China to help with North Korea, it has not worked out. At least I know China tried!” Mr Trump tweeted on the eve of yesterday’s Diplomatic and Security Dialogue.

White House officials could not clarify if Mr Trump was referring to Otto Warmbier, a US student who died this week after his release from North Korea in a coma, or the push to convince China to increase pressure on Pyongyang to abandon its nuclear programme.