South Korean Foreign Minister Park Jin said at a briefing, “The Three Nos was not a promise or agreement we made to China but an explanation of our position.”

China and South Korea on Friday clashed over Terminal High Altitude Area Defence (THAAD) system installed by the United States in Seoul after South Korea's foreign minister's visit to Beijing this week. Raising security concerns, China asserted that the THAAD's powerful radar could peer into its airspace. Chinese spokesman Wang Yi told a briefing the THAAD deployment in South Korea "undermines China's strategic security interest". US argued that the THAAD is "a prudent and limited self-defence capability" for South Korea.

The anti-missile batteries strongly opposed by Beijing first sought approval to be installed in 2016, and South Korea’s new government signalled a willingness to expand the US missile shield, thus creating differences with Beijing. Terminal High Altitude Area Defence (THAAD) is a transportable system that intercepts ballistic missiles during their final, or terminal, phase of flight. It incorporates an X-band radar, the AN/TPY-2, and a single-stage, hit-to-kill interceptor to defeat ballistic missiles inside or outside of the atmosphere, according to the CSIS Missile Defence Project.

South Korea fears that North Korea is preparing to conduct a nuclear test and hence is hesitant to reverse existing policy in a major blow to ties with PRC. Beijing, registering discontentment, suspended the Chinese group tours to South Korea and dismissed the trade and cultural imports.

New Govt Flouts 'Three NOs'

South Korea’s former president, Moon Jae-in, who had also engaged with North Korea for the normalization of ties had attempted to cement relations with Beijing by pledging the “Three Nos." The first was that Seoul wouldn’t deploy any additional THAAD systems of the United States. And that it wouldn’t participate in US-led missile defence networks or form a trilateral military alliance with Japan involved. But the new government backtracked on it saying that the Lockheed Martin Corp manufactured missile shield was “not negotiable."

South Korean Foreign Minister Park Jin said at a briefing, “The Three Nos was not a promise or agreement we made to China but an explanation of our position.”

“It is difficult to accept the call from China that we should keep the Three Nos policy even though the matter is of direct concern to our national security and sovereignty," he added.

South Korea underscored its need for self-defence, a senior presidential official told news outlets that the Yoon administration has been intending to “normalize” the operation of the US base in the southern city of Seongju that deployed the THAAD system.