Not before time Robert Gates, the US defence secretary, has impressively clarified and toughened President Barack Obama’s policy on North Korea. The United States “will not accept North Korea as a nuclear weapons state”. Washington “unequivocally” confirms its commitment to defend Japan and South Korea, but has no intention of taking military action – unless North Korea “does something that requires it”.

What might that be? Pyongyang’s latest nuclear test and rocket-launching spree had not, Gates implied, alarmed Washington as much as, perhaps, North Korea’s “dear leader” and hardline generals had expected and hoped they would.

While Pyongyang’s nuclear programme ultimately menaces world peace and the United States “will not stand idly by as North Korea builds the capacity to wreak destruction on any target in the region – or on us”, it is not yet a sufficiently clear and present threat to warrant a military response. Should North Korea attempt to sell nuclear weapons or nuclear material, however, either to states or “non-state actors”, that “would be considered a grave threat to the United States and our allies. And we would hold North Korea fully accountable for the consequences”.

Militarily, that has it about right: this is a massive provocation, not a crisis. Two nuclear tests, the first a dud, do not a nuclear power make. The regime is probably some way from getting all its nuclear ducks in a row. The flat tone adopted by Mr Gates may also be designed to persuade Beijing, whose patience with its tiresome protégé is severely frayed, that squeezing Pyongyang is less against China’s interests than doing nothing in the name of preventing a “chaotic” collapse of the regime.

North Korea most certainly has impressive missiles, the plutonium for dirty bombs and a track record of flogging whatever it has to dangerous customers. Preventing that is the priority, which means securing Chinese support for a United Nations ban on all North Korea’s weapons trade (only heavy weapons are restricted under existing UN sanctions), policing it rigorously and starving Pyongyang of revenue from exporting weapons, drugs and fake currency by reviving sanctions on banks that handle payments for it.

Politically, Mr Obama has tried the “open hand” – sending no fewer than four US delegations to Pyongyang this year – and learnt that the dictatorship is hard-wired to interpret conciliation as naivety or weakness. Mr Gates has dismissed nuclear blackmail as wholly self-destructive. Detailed policies must drive that tough message home. Ultimately the North Korean dictatorship understands only force.