Speaking a week after Mr Trump held a summit with China’s President Xi Jinping when the two leaders held discussions about North Korea, Wang Yi, the Chinese foreign minister, said the situation was on a “knife edge”.

Cautioning of the risk of a breaking storm, he urged all parties to “refrain from provoking and threatening each other . . . and not let the situation get to an irreversible and unmanageable stage.”…

Bonnie Glaser, a China expert at CSIS, a think-tank, said there were some signs of more Chinese pressure.

She pointed out that China had turned back North Korean ships carrying coal exports in line with UN sanctions, and noted tough statements in China’s semi-official media about public support for halting oil exports if the regime “makes another provocative move this month”.