beijing/seoul chinese tour operators base border city dandong tell halt trip north korean capital pyongyang five source tell reuters tuesday day u.s. president donald trump first official visit china chinese president xi jinping host trump beijing wednesday north korea development nuclear weapons expect top agenda unite state pressure china rein neighbor ally tourism one remain ways north korea earn hard currency unite nations ramp sanction country past year curb key export industries include coal seafood textiles unexpected idea go happen receive notification today say chinese tour operator run trip north korea dandong devastate news us say add order come dandong tourism bureau source reuters interview story request anonymity sensitivity issue dandong tourism bureau immediately reachable comment late tuesday china foreign ministry immediately respond request comment send work hours tuesday night tour company take chinese tourists north korea base dandong main trade hub chinese side border dandong-based tour company tell tuesday wednesday permit run one-day tour sinuiju north korean city opposite dandong popular destination chinese tourists make day trip long trip pyongyang part north korea ban notice source say many chinese tour operators run three-day long tour inside world isolate country source say government give official explanation change low season right unlikely reason say another dandong-based tourism source much likely connect increase sanction north korea wait see happen trump leave china maybe loosen rule hard say connect grow tensions early year unite state ban citizens visit north korea american college student otto warmbier die shortly return unite state coma follow year captivity north korea detain tour korea maritime institute think-tank south estimate tourism generate 44 million annual revenue north korea 80 percent north korea foreign tourists chinese say china say 237,000 chinese visit 2012 stop publish statistics 2013. order appear affect north korea-focused tour operators base elsewhere receive notice halt trip north korea say rubio chan glo travel hong kong-based tour company take tourists north korea may base hong kong work directly partner pyongyang exclusive china curb tourism north korea ahead trump visit source