North Korea has hit the button on its fifth and potentially most powerful nuclear test, claiming to have successfully tested a nuclear warhead.

In early July, South Korea decided to allow the United States to deploy the Terminal High-Altitude Area Defense (THAAD) system. At the heart of this issue is the difference in how China and the United States view the role of South Korea and decisions related to the security and stability of the peninsula.

The foreign ministers of China, Japan and South Korea put aside frictions over territorial disputes and wartime history to sharply criticize North Korea's latest submarine missile test on Wednesday in a rare display of unity.

Following months of assessment by a Joint Working Group, the U.S. Defense Department announced in July that the U.S. Forces Korea Command will station a Terminal High-Altitude Area Defense (THAAD) battery in South Korea “as a defensive measure to ensure the security of the nation and its people, and to protect alliance military forces from North Korea's weapons of mass destruction and ballistic missile threats.”

Seoul should fully understand the consequences of THAAD in the ROK, reverse the deployment decision and cooperate with countries concerned in an effort to force the DPRK to abandon its nuclear project and mitigate the tense situation in the Korean Peninsula. THAAD will only produce two winners: the U.S. and the DPRK.

The U.S. Defense Department recently announced that the U.S. Forces Korea Command will station a Terminal High-Altitude Area Defense (THAAD) battery in the Republic of Korea (ROK) as a defensive measure against North Korea. But Russian and Chinese representatives have expressed concern about how THAAD could affect strategic stability, alliance relations, and global influence.

The missile-defense deployment will worsen the bifurcation in East Asia, where regional arrangements for economic growth are shaped with China at its core while regional security architecture is set up with the US-centered military alliances as its foundation. Should this contradictory situation evolve, neither regional economic growth nor security could be sustained.

China must keep in mind its significant interests in multiple aspects of the North Korea issue, as it tries its best to balance such interests under difficult circumstances and create conditions for improving China-DPRK ties while preserving its mutual security and stability goals with Washington and Seoul.

By ignoring the Chinese, Kim Jong-un has been gambling with his regime’s future. The PRC appears more ready than ever before to abandon its troublesome friend. However, inertia—and a cold-hearted assessment of interests—is likely to hold Beijing back from cooperating with the U.S. if forced to choose America over Pyongyang.

No nuclear-weapon states have given up efforts in modernizing their arsenals, although for different reasons. A commitment of no-first-use is defensive in nature, but it doesn’t exclude nuclear retaliation. Such a pledge doesn’t cripple other countries’ nuclear capabilities: It boosts confidence that a world free of nuclear weapons is eventually possible.