North Korea announced it had successfully completed another “crucial test” at the Sohae long-range rocket launch site, as frustration grows over the lack of progress in negotiating sanctions relief with the US. “Another crucial test was successfully conducted at the Sohae Satellite Launching Ground from 22:41 to 22:48 on December 13,” a spokesman for the North’s National Academy of Defence Science said in a statement carried by the official KCNA news agency on Saturday. Read more: Opinion: What China and the Koreas can learn from German reunification He added that “research successes” will be “applied to further bolster up the reliable strategic nuclear deterrent” of North Korea. The statement did not specify what kind of test was conducted. It may have included technologies that improve missiles’ capability of reaching the US. The completion of another “very important test” had been announced days earlier. US Special Envoy on North Korea Stephen Biegun is due to arrive for a three-day visit to Seoul in South Korea on Sunday. A sinister ‘Christmas gift’ Three previous summits with US President Donald Trump have failed to deliver sanctions relief for North Korea. The country’s leader, Kim Jong Un, has threatened the US with a “Christmas gift” if concessions are not reached…