With its insistence this week that "incremental" denuclearisation by North Korea is unacceptable, the United States has signalled that it will expect Chairman Kim Jong Un to deliver on goals agreed to with President Donald Trump at the Singapore summit. After the aborted Hanoi summit that shrouded their disarmament talks in uncertainty, both sides have begun re-establishing their positions. Satellite images and the detection of an artificial earthquake suggest that North Korea could be preparing to launch a rocket or a missile, as it has done in the past to improve its leverage. Mr Trump's top nuclear negotiator, Mr Stephen Biegun, and Secretary of State Mike Pompeo restated on Monday Washington's unwillingness to lift sanctions before Pyongyang denuclearises. It was reportedly Mr Kim's desire for immediate relief from sanctions that led to the rupture in Hanoi.

The Singapore summit was remarkable in that it came close to a public acknowledgement from North Korea that it could not simultaneously pursue nuclear weapons and economic development. It was an about-turn from 2013 when Mr Kim declared before the United Nations that a trade-off was not necessary. Then, for reasons not yet clear, Mr Kim agreed in last year's breakthrough meetings - first in Panmunjom and then in Singapore - that North Korea would step off the nuclear path if it received security guarantees, including the winding up of US-South Korea joint military exercises, and relief from sanctions that have kept its economy hostage. But a matter of sequencing, whether denuclearisation is to follow easing of sanctions or precede it, bedevils that agreement.