seoul north korea congratulate china 19th communist party congress wednesday amid increasingly fray relationships traditional ally china tighten sanction pyongyang nuclear weapons program central committee north rule workers party korea say china make great progress accomplish cause build socialism chinese characteristics correct guidance communist party greatly please party central committee say message carry official kcna news agency add sincerely wish china congress satisfactory success chinese foreign ministry spokesman lu kang say many foreign political party organizations dignitaries send congratulations include workers party korea show international community pay close attention 19th party congress express thank lu tell daily news brief officials experts south korea worry pyongyang may conduct weapons test coincide open twice-a-decade congress beijing sign chinese president xi jinping give open speech unite state ally many people china believe beijing rein pyongyang acceleration north korea nuclear missile capabilities coincide near-total breakdown high-level diplomacy two china pyongyang sole major ally account 90 percent world trade isolate country say strictly enforce u.n. security council sanction ban import coal textiles seafood cut oil shipments north amid strain tie north korea congratulate china party congress