The National Assembly's foreign affairs committee is set to convene a plenary session on Tuesday afternoon to question the foreign ministry about Seoul and Tokyo's negotiation prior to Japan's Sado mines being designated a UNESCO World Heritage site.

The Sado mines, where Koreans were forced into labor during Japan's colonial rule, received the UNESCO designation late last month.

The main opposition Democratic Party(DP), which has questioned whether Seoul sufficiently demanded Tokyo to include the term "forced labor" in its efforts for the UNESCO registration, is expected to grill ministry officials about the matter, as well as an intervention by the presidential office.

Representatives from the DP, as well as the minor Rebuilding Korea Party and Jinbo Party also plan to visit the Sado mines marking Liberation Day on Thursday, and demand the Japanese government's inclusion of "forced labor."