North Korea marked the start of the advent season on Tuesday with the promise of a “Christmas gift” for the US if it made no progress on reviving stalled nuclear talks in December. In April, Kim Jong-un, the North Korean leader, set an end-of-year deadline for Washington to show flexibility in its position, but US officials have described the deadline as artificial, appearing to wave off its significance. The past few months have been marked by a series of North Korean weapons tests, widely viewed as a sign of Pyongyang’s growing frustration at failed international efforts to resume talks after the collapse of a February summit in Hanoi between Kim and Donald Trump, the US president. In the latest statement from Pyongyang, one of several warnings issued via state media, Ri Thae Song, vice minister of foreign affairs, in charge of US relations, accused Washington of trying to drag out denuclearisation talks ahead of the US presidential election next year. The thre...