China’s stance aligned with North Korea on Thursday, December 25, 2025, regarding the recent entry of a US nuclear-powered submarine into South Korea. This came especially after the US approved South Korea’s efforts to acquire its first nuclear submarine and the establishment of a US-South Korean military partnership, which, from both the US and South Korea’s perspective, functions as a joint military alliance against the perceived Chinese threat. This Chinese escalation coincided with Washington and Seoul’s announcement in December 2025 of the commencement of formal negotiations for a treaty that would allow South Korea to build nuclear-powered submarines. At this juncture, China’s security, military, and intelligence agencies expressed solidarity with North Korean leader Kim Jong-un, arguing that South Korea’s plan to build nuclear-powered submarines would exacerbate instability in the region and pose a threat to North Korea’s national security.
China’s categorical rejection of the arms deal between Washington and Seoul stemmed from the fact that these American nuclear submarines would grant the South Korean navy a greater role, not only regionally but also globally. China warned South Korea that it would bear responsibility for the global deployment of these submarines, given the threat they posed to China’s regional security, particularly in Southeast Asia. The US Department of Defense responded to these Chinese accusations by emphasizing that the US-South Korea partnership is essential to countering China’s activities in the “gray zone” and to strengthening deterrence mechanisms against China and its threats, especially in the South China Sea. This comes amidst growing US provocations against Beijing, including the possibility of joint naval exercises in the Yellow Sea near China’s borders.
China and North Korea condemned Seoul’s plan to build nuclear-powered submarines, arguing that it would increase instability on the Korean Peninsula. Both China and its ally, North Korea, consider it an act of aggression that severely violates their security and maritime sovereignty.
Given the growing military cooperation between the United States and South Korea in areas such as naval shipbuilding and capacity building, the monitoring of threats posed by North Korea (a Chinese ally) to its southern neighbor, and Washington’s arming of Seoul, particularly in the field of underwater military technologies for uninhabited areas,
China’s Foreign Ministry called on both the United States and South Korea to uphold their international non-proliferation obligations and to handle these issues with caution. It asserted that these actions serve the strategies of superpowers rather than the genuine security interests of the surrounding Asian region.
Based on this growing nuclear military cooperation between Washington and Seoul, China, in December 2025, took a strong stance against the presence of US nuclear submarines in South Korea, whether through docking at ports or through cooperative plans to build domestic nuclear submarines for Seoul. The main points of China’s current stance on the US-South Korean nuclear submarine deal can be summarized as follows: China warns against nuclear proliferation on the Korean Peninsula. Beijing has expressed strong opposition to cooperation between Washington and Seoul on nuclear-powered submarines, warning that it could undermine the global nuclear non-proliferation regime. China also objects to the potential for this to fuel an arms race in the Asian region. Chinese experts and officials believe that these moves, such as the entry of US attack submarines into the port of Busan, as occurred in December 2025, threaten regional peace and stability and could lead to an arms race in the region. Furthermore, from a Chinese military perspective, this represents criticism of what they perceive as double standards in dealing with Beijing. China likens the current US-South Korean cooperation model to the “Quadrilateral Aukus Nuclear Cooperation (QNCC) agreement” with Australia, South Korea, Japan, and India, which China considers a dangerous precedent demonstrating the US’s coddling of its allies by providing them with military nuclear technology, thus weakening the Treaty on the Non-Proliferation of Nuclear Weapons.
Therefore, China has affirmed its complete readiness to counter such US military attempts with South Korea, given the threat they pose to China’s security, which must be addressed. Chinese military officials have warned that China will firmly and resolutely uphold its national security policy and the principle of deterring the enemy. Official Chinese sources have stated that the enemy will undoubtedly pay a heavy price for violating the strategic sovereignty and security of China and its allies and will face retaliatory attacks if it chooses the military option against Chinese targets and interests. The Chinese Ministry of Defense has emphasized that Beijing will continue to demonstrate its capabilities in confronting this blatant aggression against its sovereignty and that this is part of China’s responsible practice of genuine nuclear war deterrence and a reliable shield for defending China’s national sovereignty. With China clarifying that its military forces aim to ensure a peaceful and secure environment, North Korea responded in solidarity with China by showcasing its nuclear submarines. North Korea asserted that these new nuclear submarines represent a decisive historical shift in its deterrent capabilities against potential aggression from Washington and Seoul.
Therefore, China condemned this provocation, which it described as a US-led mobilization and militarization of the region through its allies, such as South Korea, posing a serious security threat to the Korean Peninsula. The Chinese People’s Liberation Army and Ministry of Defense also rejected the US military’s claims that South Korea’s nuclear submarines, acquired with US assistance, are a necessary US military measure to counter the perceived Chinese threat to the Korean Peninsula.
