By Yi Wonju SEOUL, Dec. 31 (Yonhap) North Korean delegates participating in an upcoming congress of the ruling Workers Party have gathered in Pyongyang and were awarded certificates, state media said Thursday, raising the possibility that the meeting could take place as early as this week. The upcoming session, which will be the first party congress in four years, has drawn keen attention as the North is expected to unveil a new economic development plan and could announce its new policy line on the United States and South Korea. Delegates to the 8th Party Congress arrived in Pyongyang late in December amid the warm welcome by citizens, the official Korean Central News Agency (KCNA) said.