The belligerent unilateralism of Donald Trump’s foreign policy has a notable exception in the US president’s approach to North Korea. Mr Trump’s initial threats to heap fire and fury on Kim Jong Un’s regime have made way for sustained diplomacy to persuade Pyongyang to give up its nuclear ambitions. Ahead of a second summit set for later this month in the North Vietnamese capital of Hanoi, Mr Trump has expressed confidence that Mr Kim has switched focus from nuclear weapons to economic modernisation.

The first meeting between the two leaders in Singapore last June produced encouraging atmospherics, but limited practical results. The summit has been followed by North Korea’s suspension of underground nuclear explosions, and of the testing of missile systems. Pyongyang has also destroyed a nuclear test site. Mr Trump in return has dropped joint US-South Korean military exercises. Moon Jae-in, the dovish South Korean president, has taken the opportunity to warm relations with Pyongyang.

Missing, however, has been any real sign that Mr Kim is prepared to dismantle the country’s nuclear capability. Western intelligence estimates suggest the regime already has a stockpile numbering several dozen warheads. It may also be sufficiently advanced in its long range missile programme to be relaxed about suspending flight tests. So Washington has since maintained its sanctions against the regime and Mr Kim has insisted the world should not expect unilateral measures to degrade his nuclear capability.