The cost could rise to up to 222.1 billion won if South Korea pays 5 percent fees on gas equal to 7.5 million tons from Russia's Far East to South Korea via North Korea for a period of 30 years.

   KOGAS said it is hard to estimate the exact amount of transit fees as it needs to conduct a geological survey before building the infrastructure and calculate natural gas demand in North Korea.

   "Once international sanctions on North Korea are lifted in the future, we will decide whether to push for the trans-Korea natural gas pipeline project after reviewing its feasibility, stability of gas supply and diplomatic and security issues," KOGAS said in the report.

   South Korea, the world's third-largest buyer of natural gas, has sought to stably bring in fuel at cheaper costs for the past 20 years, but such efforts have not materialized due in part to security tensions on the peninsula.

   The project is now part of Seoul's "New Northern Policy," which is aimed at expanding economic cooperation with Russia in energy, transportation and various other areas. (Yonhap)