WASHINGTON • In the giddy days of June 2018, as American President Donald Trump and North Korea's Chairman Kim Jong Un met in Singapore, it seemed for a tantalising moment that the sceptical Korea experts at the think-tanks here were wrong, and an unconventional, norms-breaking president was on the brink of an outstanding breakthrough.

In the run-up to the Singapore summit, Mr Raj Shah, then White House deputy spokesman, was asked by a reporter if the administration had consulted with well-known Korea experts such as former CIA North Korea analyst Sue Mi Terry (now with the Centre for Strategic and International Studies and former ambassador, congressman and governor Bill Richardson).