The missile intercept system is designed to defend against North Korea's evolving missile capabilities, but China has vehemently protested the decision which it said would compromise Beijing's national interests in the region.

Since mid-2016, China has taken a series of what Seoul considers as retaliatory measures in protest, banning South Korean entertainers from performing in the Chinese market and imposing prohibitively stricter import standards on popular South Korean trade goods, including cosmetics and batteries of electric cars.

South Korea is trying to make the case that the actions taken by the Chinese government constitute unfair retaliation that can be sent to the WTO for arbitration. "It's not an easy process to say exactly what WTO rules are in breach," the official said.

The South Korean government, moreover, is trying to determine which actions taken by Beijing were in retaliation for THAAD or part of a growing discriminatory treatment of foreign companies in general, the official added. (Yonhap)