U.S. officials on Tuesday offered “strong support” for a previously-delayed joint survey on inter-Korean rail cooperation, South Korean chief nuclear envoy Lee Do-hoon said.The comments followed the launch of a U.S.-ROK working group on DPRK issues in Washington DC, led by Lee and U.S. Special Representative on North Korea Stephen Biegun.“The U.S. side expressed full and strong support for the joint survey of inter-Korean railway lines,” Lee said at a press conference following the meeting in a statement carried by Seoul's Yonhap News Agency.The South Korean government previously admitted to differences with