Keeping Southeast Asia open for business is a geopolitical task as much as a commercial one. Its relationships across geopolitical divides give companies access to competing powers’ markets, capital, and technology. In 2025, ASEAN attracted a record $243.9 billion in foreign direct investment. But conflict, U.S.-China strategic competition, and economic nationalism threaten these opportunities. Sustaining them requires protecting the security, supplies, and rules underpinning commerce. Governments must de-escalate tensions and, with businesses, understand and address the political objectives behind economic restrictions, assess whether diversification reduces vulnerabilities or creates new ones, and strengthen critical infrastructure. They have a shared interest in defending international law—even when doing so may create friction with the country violating it. Conflict and coercion  The U.S. war against Iran has disrupted oil and gas supplies to Southeast Asia, which relies heavily on the Middle East. Higher energy prices raise business costs, squeeze household budgets, and increase loan-default risks. The Strait of Hormuz has also demonstrated how a strategic waterway can become an instrument of coercion, even for a militarily weaker power. Developments there serve as a stark warning about the risks of coercion and disruption in the Straits of Malacca and Singapore. In August, Indonesia, Malaysia, and Singapore reaffirmed their commitment to keeping those waterways, which carry nearly a quarter of global seaborne trade, free, open, and safe. That commitment does not preclude a littoral government restricting passage, an outside power pressuring it to do so, or a state or non-state actor disrupting shipping. Economic détente between Washington and Beijing could benefit businesses, but if maintaining it diminishes U.S. commitment to regional security, it could weaken deterrence and undermine the stability commerce depends on. In October 2025, China began its first significant island-building in the South China Sea in almost a decade at Antelope Reef, where it is building a runway; the reef is now China’s largest outpost in the disputed Paracel Islands. In September, China announced the opening of a joint military aviation facility in Laos. China has also expanded its presence in the waters east of Taiwan, where Japan and the Philippines have overlapping exclusive economic zones. A shift in the regional balance of power could increase vulnerability to coercion and affect the rules governing trade and investment. Strategic rivalry and economic nationalism  Strategic rivalry has brought gains for Southeast Asian countries able to maneuver for advantage: higher U.S. tariffs on Chinese goods prompted manufacturers to shift production to the region. But U.S. licensing requirements for shipments of certain advanced chips to China can delay or prevent sales by regional distributors. Malaysia, amid U.S. pressure, introduced its own controls, including 30-day advance notification for specified advanced chips moving through or out of the country. U.S. economic nationalism creates a distinct challenge: Washington’s drive to reduce trade deficits and rebuild American manufacturing extends beyond its rivalry with Beijing. Tariffs have applied across Southeast Asia, including to U.S. allies and partners—even Singapore, with which the United States runs goods and services surpluses. Vietnam, which ran a $178.3 billion goods surplus with the U.S. in 2025, has drawn particular scrutiny. Legal challenges have not ended this pressure. After the U.S. Supreme Court’s February ruling that the emergency law did not authorize Trump’s “Liberation Day” tariffs, the administration turned to temporary tariff powers and Section 301 investigations into alleged excess manufacturing capacity and failures to adopt or enforce bans on imports made with forced labor. The latter led to July tariffs on all 60 economies investigated, including several in Southeast Asia. Understanding Washington’s objectives and priorities helps determine what concessions might achieve. The administration has justified tariffs and other restrictions by citing reciprocity, reducing deficits, protecting domestic industry, raising revenue, reducing strategic dependence, and denying capabilities to a rival. Trade concessions may not remove restrictions designed to deny China strategic capabilities. Nor will moving production from China to Vietnam satisfy demands for production in the United States. Unclear or conflicting priorities will complicate responses. Assess dependencies Securing multiple suppliers may reduce vulnerabilities, but those suppliers may still rely on the same shipping routes or Taiwanese semiconductor foundries. The region remains acutely exposed to energy supply disruptions. Businesses cannot yet count on regional arrangements to secure supplies. The revised ASEAN Framework Agreement on Petroleum Security has yet to enter into force; even once it does, assistance during critical oil and gas shortages will remain voluntary and subject to commercial terms. The ASEAN Power Grid could diversify electricity supplies, but a regional system remains elusive nearly three decades after ASEAN leaders called for it. Nuclear power could reduce fossil-fuel dependence for electricity generation. Vietnam has signed an agreement with Russia for its first plant; an Indonesian company has agreed to buy electricity from two Rosatom floating nuclear units. The Philippines has discussed nuclear cooperation with Russia. Russian reactors, however, could create long-term dependence on Moscow for technology, nuclear fuel, spare parts, and technical support. Energy insecurity has lent urgency to Philippine-Chinese talks on joint oil and gas development in the South China Sea. Yet any deal’s benefits must be weighed against its implications for Philippine maritime rights and potential dependence on Beijing. Strengthen systems and uphold rules Resilience can contribute to deterrence by reducing what hostile actors expect to gain from disruption. Governments must work with owners and operators to strengthen critical infrastructure, including subsea cables, ports and data centers. A World Economic Forum report to which I contributed advocates joint vulnerability assessments, standards setting, communication mechanisms, and response planning. The rules underpinning commerce also need defending: economic rules provide predictability and recourse, while international law protects freedom of the seas and constrains the use of force. Upholding international law may cause friction, but countries should remain steadfast. Not wanting to choose sides should not be an excuse for failing to defend the rules: this is not about alignment with any country. Keeping Southeast Asia’s commercial options open will require taking a stand to defend rules that support peace and prosperity. Lynn Kuok will be speaking at the Southeast Asia 500 Summit on Nov. 3 in Ho Chi Minh City, Vietnam. Join executives from the Fortune Southeast Asia 500, policymakers, and investors to examine the forces reshaping one of the world’s most important growth regions. Apply here. The opinions expressed in Fortune.com commentary pieces are solely the views of their authors and do not necessarily reflect the opinions and beliefs of Fortune. 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