The script has been followed so closely over the past seven years that it is easy to shrug off the sequence of events with nonchalance. North Korea provokes with nuclear or missile tests, sanctions are imposed against its regime and Pyongyang rains down threats of war on its perceived enemies. The world has frustratingly been here too many times before and a new approach has to be found. China and the US, being key to any deal, have to work together to make it happen.

They did that in formulating the latest UN Security Council sanctions, imposed last Friday after a third nuclear test. North Korea's ruling class is again targeted, financial and travel restrictions being tightened and nations banned from exporting luxury goods. UN diplomats portrayed the resolution, the fifth since 2006, as sending a tough message to the North. The response was predictable: a rejection of attempts to end its nuclear programme and a barrage of war words at the US, the perceived chief protagonist. This, as the US and its ally, South Korea, began annual joint military drills.

China, the North's closest ally, will not abandon its neighbour. But as Beijing's support for the two latest UN resolutions proves, it is also losing patience. A solution requires striking a balance; putting too much pressure on ruler Kim Jong-un's regime could cause it to collapse, potentially creating a flood of refugees. Instead of deepening isolation and economic hardship, there has to be diplomacy and dialogue.