US academics and former senior officials met North Korea’s chief nuclear negotiator Ri Yong Ho in Singapore yesterday to get a feel for each other’s positions on Pyongyang’s nuclear missile programmes.

Leon Sigal, who is director of the Northeast Asia Co-operative Security Project at the Social Science Research Council NGO, explained: “It’s two ways of taking each other’s temperature.”

The US and North Korea have no formal diplomatic ties, but former US officials occasionally meet Pyongyang diplomats.