US Republicans' Warning to South Korea on China: Semiconductors and South Korea-China Relations Put to the Test Again

Executive Summary

John Moolenaar, Chairman of the House Select Committee on the Strategic Competition Between the United States and the Chinese Communist Party, sent a letter to Secretary of State Marco Rubio raising concerns over South Korea-China relations and the Chinese production facilities of Samsung Electronics and SK Hynix, just ahead of President Trump's announcement of large-scale South Korean investments. This highlights a dual-track structure where congressional hawks seek to tighten surveillance on allies even as the Trump administration adopts a conciliatory stance toward China through summit diplomacy with President Xi Jinping. By simultaneously raising the security frame of semiconductor export controls and the trade frame of discriminatory treatment against US companies, the letter is highly likely to be repeatedly invoked in administrative procedures, such as future Validated End-User (VEU) status renewal reviews. While steadfastly pursuing the implementation of investment agreements, including the Alaska LNG project, South Korea needs to separate its responses: adopting a fact-based, low-key approach to security issues, and an offensive approach prioritizing transparency for trade issues. Given that this is a structural risk originating from Congress that cannot be resolved solely by managing executive channels, companies must also strategically reassess their production facilities in China.

I. Analysis of the Current Situation

US Republicans' Public Warning on South Korea's Relations with China: Situation Analysis

1. Background and Developments

South Korea and the United States are currently in the phase of executing investment projects under the trade agreement signed last year. President Trump was scheduled to announce South Korean investment projects in the US, including the Alaska LNG project [15]. Around September 30, the White House was preparing to announce South Korea's $200 billion energy investment [9]. Coinciding with this announcement, Representative John Moolenaar, Chairman of the House Select Committee on the Strategic Competition Between the United States and the Chinese Communist Party, sent a letter to Secretary of State Marco Rubio [9].

Chairman Moolenaar's raising of these issues is not new. Since the Biden administration, the United States has utilized technology controls against China in semiconductors, 5G, AI, and batteries as tools of economic security [3]. The policy of countering China by restructuring supply chains with allies and partners has continued regardless of the change in administration [3]. In this process, South Korea has been pressured to make tilted choices between its military ally, the United States, and its largest trading partner, China [3]. This letter is an example showing that such structural pressure persists into the second Trump administration.

At the same time, US-China relations are tracing a different trajectory from Chairman Moolenaar's hardline stance. On September 23, President Trump personally welcomed President Xi Jinping at Joint Base Andrews for his state visit to the US [11]. The two countries established the US-China Trade Committee during their Beijing summit in May, and USTR Representative Greer announced plans to continue promoting balanced trade and expanding trade in non-sensitive items [2][8]. A paradoxical dynamic is emerging where, even as the Trump administration's approach to China leans toward conciliation, congressional hawks on China are demanding tighter surveillance on allies [12].

2. Current Situation

In his September 29 letter, Chairman Moolenaar premised that South Korea is a "key US ally" but argued that changes in South Korea-China relations could pose "significant risks" to the United States [1]. According to reports citing Reuters, he raised issues regarding South Korea-China summit exchanges, South Korean companies' semiconductor investments in China, South Korea's readiness in the event of a Taiwan contingency, and the South Korean government's regulatory approach toward US and Chinese companies [1].

Specifically, pointing to Samsung Electronics' Xi'an plant and SK Hynix's Wuxi and Dalian production facilities, he warned that such investments could give Beijing leverage over the allies' technology supply chains [4]. He noted that friction between the US and South Korea "has the potential to develop into a structural shift in Seoul's alignment, requiring close monitoring and, if necessary, coordinated action" [4]. According to an Al Jazeera report, in the same letter, he also criticized South Korea for treating US companies discriminatorily compared to China-linked competitors [9]. Yonhap News' Washington correspondent also reported on the letter as a demand for "heightened vigilance," confirming that it urged Secretary Rubio to maintain continuous oversight [7].

This letter was made public just before President Trump's announcement of South Korean investments [9]. Coincidentally, as the investment announcement and Congress's warning to counter China overlapped in the same week, some in South Korea view them not as separate issues but as linked pressure signals [1].

3. Key Actors and Positions

Chairman John Moolenaar and the House Select Committee on the CCPview the allies' exposure to China in the semiconductor supply chain as a strategic vulnerability [4]. Representing a manufacturing-heavy district in Michigan, Moolenaar leads the committee, which, despite its bipartisan composition, has been driven by a Republican chair leading the hardline stance on China. His demand takes the form of requesting enhanced oversight from the State Department, suggesting an indirect check through public relations and legislative pressure rather than direct intervention in executive policy [1].

The State Department and Secretary Rubioare the recipients of the letter but have not yet issued a public response. Given that the Trump administration's stance on China has entered a phase of relaxation following the summit, the State Department has limited incentive to immediately translate Chairman Moolenaar's demands into policy [11][12].

The USTR and Representative Greerare pursuing the expansion of US-China trade in non-sensitive items and the implementation of the US-China Trade Committee's recommendations on a separate track [2][8]. This highlights a gap between the congressional hawks' demands to counter China and the pragmatic approach of the administration's trade officials.

The South Korean Governmentreceived this letter just as it was preparing to announce investments in the US, including the Alaska LNG project [15][9]. Since the operation of Samsung Electronics' and SK Hynix's production facilities in China was publicly brought into question, the South Korean government and the companies involved are increasingly likely to face pressure to scale back their semiconductor investments in China [4].

Chinahas not yet officially reacted to this matter, but the very fact that the South Korea-China semiconductor supply chain linkage was identified as leverage by the US Congress could be utilized in Beijing's leverage narrative toward South Korea.

4. Key Issues

The first issue is the policy inconsistency arising from the simultaneous demands for implementing the US-South Korea investment agreement and countering China. The situation where the White House accepts tens of billions of dollars in South Korean investments while Congress takes issue with South Korea's exposure to China makes it difficult for South Korea to determine which signal to prioritize [9][15].

The second issue is the future operational direction of Samsung Electronics' Xi'an plant and SK Hynix's Wuxi and Dalian plants. These facilities represent existing investments that have been operational for years, and an immediate withdrawal or downsizing is technically and economically complex [4].

The third issue is the fragmentation of the policy-making line within the United States. With President Trump and USTR Representative Greer's conciliatory stance toward China coexisting alongside the countering stance of congressional hawks like Chairman Moolenaar, the signals South Korea must respond to are not unified [11][12]. This increases uncertainty for the South Korean government and businesses regarding which demands they should align with when adjusting their China strategies.

The fourth issue is the new framing of "discriminatory treatment of US companies." While previous discussions focused on semiconductor export controls and supply chain security, this letter shifts the focus to South Korea's domestic regulatory framework itself as an issue of reverse discrimination against US firms [9]. This suggests that future US-South Korea trade consultations could put domestic regulatory and procurement practices on the agenda, moving beyond semiconductor investment issues.

II. In-Depth Analysis of the Issue

US Republicans' Public Warning on South Korea's Relations with China: In-Depth Analysis

1. Root Cause Analysis

As Chairman of the House Select Committee on the CCP, Moolenaar has for years championed semiconductor export controls and the tightening of outbound investment screening as legislative agendas. The targets of this letter are Samsung Electronics' Xi'an plant and SK Hynix's Wuxi and Dalian production facilities [4]. These facilities are assets that have already been granted a certain level of exception under the US Department of Commerce's export control system through "Validated End-User (VEU)" status. Chairman Moolenaar raising issues with them again can be read as pressure from the legislature to review the very exceptions granted by the executive branch.

The issues raised in the letter fall into three main categories: South Korea-China summit exchanges, semiconductor investments in China, and the South Korean government's differential treatment of US and Chinese companies [1]. Among these, the final issue of "discriminatory treatment" was elaborated in the Al Jazeera report. He specified that South Korea treats US companies less favorably than China-linked competitors [9]. This indicates that grievances have accumulated within Congress that South Korea's industrial regulations or antitrust enforcement operate to the disadvantage of US firms in certain sectors. A defining feature of this issue is that the security frame of semiconductor export controls and the trade frame of market access for US companies are intertwined within a single letter.

2. Structural Context

The US effort to counter China operates under a dual-track structure where the executive branch and Congress move at different speeds and under different logics. On September 23, President Trump personally welcomed President Xi Jinping at Joint Base Andrews, and is pursuing the expansion of trade in non-sensitive items through the US-China Trade Committee established during the Beijing summit in May [11][2][8]. USTR Representative Greer stated, "Building on the strong relationship between President Trump and President Xi, both nations are deepening engagement to promote reciprocal trade" [2]. The executive branch places weight on managing relations with China centered on trust and transactions between the two leaders.

On the other hand, congressional hawks, represented by the House Select Committee on the CCP, operate independently of this conciliatory tone. While claiming a bipartisan nature, the committee has practically driven the containment of China in advanced technology sectors like semiconductors and AI, regardless of party lines. At the very moment President Trump seeks to lower the temperature of China relations through summit diplomacy with President Xi, Congress refuses to loosen its grip on countering China, instead expanding its surveillance network toward allies [12]. This discord reduces predictability from South Korea's perspective. Even if progress is made in negotiations with the executive branch, a single letter from Congress can repoliticize the same issue.

From a security structure perspective, this letter is an extension of the approach that uses the semiconductor supply chain as leverage for alliance management. Chairman Moolenaar explicitly stated that South Korea's semiconductor investments in China "could give Beijing leverage over the allies' technology supply chains" [4]. He went so far as to express that friction between the US and South Korea "has the potential to develop into a structural shift in Seoul's alignment" [4]. This perspective reframes South Korea's semiconductor investments in China not as simple business decisions but as an indicator of alliance loyalty. The inclusion of South Korea's readiness in a Taiwan contingency in the letter demonstrates the congressional hawks' perception, which directly links semiconductor supply chain issues with Taiwan Strait security scenarios [1].

In the economic structure, it is significant that the timing of the letter's release coincided with the expansion of South Korea's investments in the US. President Trump was scheduled to announce South Korea's $200 billion energy investment in the US, including the Alaska LNG project [9][15]. In the letter sent just before this announcement, Chairman Moolenaar described the US-South Korea alliance as "indispensable" while simultaneously urging vigilance against China [9]. Ramping up pressure just before the investment announcement can be interpreted as an attempt to leverage South Korea's investment implementation phase to extract further concessions regarding its relations with China.

3. Comparison with Historical Precedents and Similar Cases

This is not the first time South Korea has been forced to choose between its military ally, the United States, and its largest trading partner, China. During the Biden administration, technology controls against China in semiconductors, 5G, AI, and batteries served as key variables in US-South Korea economic relations [3]. At that time, the United States incentivized domestic production through the CHIPS and Science Act and the Inflation Reduction Act, while simultaneously pressuring allies and partners to restructure supply chains [3]. Assessments that South Korea's economic diplomacy had tilted toward its military ally, the United States, rather than China following the trade war had already emerged during that period [3].

The US-South Korea friction surrounding the 2019 notification of GSOMIA termination shows a similar pattern. At the time, some in US political and policy circles defined this as an "abuse of the alliance" and questioned South Korea's strategic choices [6]. However, from a local South Korean perspective, counterarguments were raised that this was a signal to draw US intervention into Japan's export restrictions [6]. Professor Leif-Eric Easley pointed out that "failing to fully understand South Korea's perspective and overinterpreting certain events could undermine the very trust between the US and South Korea that alliance managers have worked so hard to preserve" [6]. The same critical awareness can be applied to the Moolenaar letter. It points out that concluding South Korea's participation in RCEP or defense exchanges with China as a "tilt toward China" was an interpretive excess that has been repeated in the past [6].

Structurally, this issue is part of a continuous pattern where the United States redefines the investment decisions of an ally's individual companies as national security matters. Samsung's and SK Hynix's Chinese plants are assets that cannot be relocated in the short term due to China's massive memory semiconductor market and existing production infrastructure. Defining the investments of private companies facing such structural constraints as security risks is an approach that was repeated during past demands to exclude Huawei equipment and during semiconductor equipment export control phases. However, this case is unique in its timing, as Congress—rather than the executive branch—raised the issue, and did so during a phase when relations with China are easing through summit diplomacy.

4. Key Variables Shaping Future Developments

The first variable is the State Department's actual level of response. The key is whether Secretary Rubio will respond to Chairman Moolenaar's demands by initiating concrete investigations or pressure measures, or whether he will limit his response to a principled reply. With the Trump administration's stance on China centered on summit diplomacy, the State Department has little incentive to fully accept the demands of congressional hawks [2][11]. However, since semiconductor export controls fall under the jurisdiction of the Department of Commerce, the possibility remains that separate measures could be taken at the Commerce level even if the State Department responds passively.

The second variable is the speed of South Korea's investment implementation in the US and its corresponding reciprocity. If the announcement of the $200 billion energy investment actually leads to concrete projects such as the Alaska LNG project, it could serve as a signal that South Korea is showing good faith toward US demands [9][15]. If investment implementation is delayed or scaled back, it could provide hawks like Chairman Moolenaar with a pretext for further offensives.

The third variable is the continuity of US-China summit diplomacy. If President Trump continues to manage relations with President Xi amicably, the congressional hawks' pressure on allies is highly likely to remain a minority opinion at odds with the administration's stance [11][12]. Conversely, if a catalyst arises that worsens bilateral relations again, such as US-China tensions over the Iran issue, demands for alignment on allies, including South Korea, could gain traction at the executive level as well [10][13]. For now, the dual-track structure in which the conciliatory tone in US-China relations and Congress's hardline stance coexist is highly likely to persist for the time being.