Seoul, Jan. 23 -- US Under Secretary of Defence for Policy Elbridge Colby is set to visit South Korea early next week to probably discuss issues like South Korea's push for nuclear-powered submarines and the issue of the US' transfer of wartime operational control to Seoul, sources told Yonhap News Agency on Friday.

Colby is expected to make a three-day visit to Seoul through Tuesday on a trip to Asia that also includes a stop in Japan, according to the sources.

Alliance issues, such as a hike in South Korea's defence spending, the conditions-based handover of wartime operational control from the United States to South Korea and Seoul's push to build a nuclear-powered submarine, are likely to be discussed in his upcoming trip.

He is al...