In Brief
Southeast Asian nations are reassessing the United States as a security partner amid growing geopolitical uncertainty and volatility in US politics. But China’s continued assertiveness in the South China Sea limits Beijing’s ability to win regional trust. Southeast Asian countries are deepening economic and security cooperation with middle powers as they seek to preserve strategic autonomy and reduce dependence on either superpower.
With Washington and Beijing both raising security anxieties in Southeast Asia, countries in the region are diversifying their economic and security cooperation with middle powers.
In May 2026, Yusril Ihza Mahendra, Indonesia’s Coordinating Minister for Law, Human Rights, Immigration and Corrections, stated that Indonesia, with its abundant energy and mineral resources, could become the next ‘target’ of the United States after Venezuela and Greenland. He added that US forces in Guam could reach Papua within six hours and that in the event of war, the Indonesian Military could ‘only last four days’.
In February 2026, an official Vietnamese document titled The 2nd US Invasion Plan was leaked to the public. Originally completed in August 2024, the document states that ‘due to the United States’ belligerent nature, Vietnam needs to be vigilant to prevent the United States and its allies from creating a pretext to launch a war of aggression’.
While these two examples may not represent the military outlook of all nations in Southeast Asia, they show that some countries in the region increasingly view the United States as a security threat, rather than a partner. This phenomenon aligns with the 2026 ISEAS State of Southeast Asia Survey, which found that more than half of respondents (51.9 per cent) identified US leadership under President Donald Trump as their top geopolitical concern.
This geopolitical turn under President Trump represents a significant change in Southeast Asia’s security landscape. China has long been perceived as the principal threat to regional stability due to its actions in the South China Sea. Many Southeast Asian countries have strengthened their security cooperation with Washington as a counterweight to Beijing.
This security cooperation, whether through joint exercises, joint patrols or defence cooperation agreements, not only increases security capabilities for participating nations, but also ensures US support in facing China’s aggressive behaviour in the South China Sea. For the Philippines, its alliance with the United States provides a potential security guarantee if tensions with China escalate.
Uncertainty under President Trump has altered Southeast Asia’s geopolitical landscape. Even after Trump leaves office, Southeast Asian countries will have learned that there is structural uncertainty in US politics. This will lead some countries in the region to reconsider the reliability of US support if a conflict occurs with China, but also, more significantly, to view the United States as a threat and a destabilising factor in regional security. China is likely to exploit this increasing regional distrust towards the United States to advance its interests.
Yet even though the ISEAS survey shows that the United States is a geopolitical concern, China’s encroachments into the exclusive economic zones and continental shelves of Southeast Asia’s littoral states remain a source of unease for the region, cited by 51.7 per cent of respondents. China will most likely put forward its agenda for joint development with countries like Indonesia and the Philippines, using grey-zone tactics to avoid legal certainty and advance its illegal claims.
Over the first half of 2026, China attracted several of the world’s most powerful leaders to visit Beijing, including US President Donald Trump, Russian President Vladimir Putin, UK Prime Minister Keir Starmer and Spanish Prime Minister Pedro Sanchez. This has put China at the centre of geopolitics and, even more so, at the centre of regional economic cooperation. With China remaining one of Southeast Asia’s largest investors and trading partners, it will likely continue to play an increasingly significant role in the region.
But with conflict in the South China Sea ongoing, China will struggle to win the region’s full trust. Southeast Asian countries are therefore likely to deepen cooperation with middle powers such as Australia, Japan, Canada and South Korea, both on economic and security issues. In the future, the region will have additional avenues to strengthen multilateral cooperation with like-minded countries, rather than being trapped between double threats from Washington and Beijing.
Jakarta has intensified its security cooperation with middle-power countries. In February 2026, Indonesia and Australia signed a new treaty on common security to increase security ties. Indonesia has also sought to diversify its defence industry procurement from various countries, including France, Turkey and South Korea. During a visit to Japan in June 2026, Malaysian Prime Minister Anwar Ibrahim also committed to strengthening cooperation with Japan on energy security, maritime security and critical minerals.
This hedging strategy is not without security risks. Both Beijing and Washington will pressure Southeast Asian countries to fall under their influence. In Indonesia’s case, Washington has pushed Jakarta to adopt policies that benefit US interests, from granting US aircraft blanket access to Indonesian airspace or allowing its infrastructure to host maintenance, repair and overhaul operations for US naval and air force assets. At the same time, China has pushed for joint development in the North Natuna Sea.
Without a clear strategy, this pressure from both sides could undermine ASEAN centrality. If US–China rivalry continues to intensify, Southeast Asian countries will have stronger incentives to deepen security cooperation beyond both Washington and Beijing.
About the author
Dr. Aristyo Rizka Darmawan is a non-resident Senior Research Fellow, Assistant Professor of Law at Universitas Indonesia, PhD Scholar at the Australian National University and Research Fellow with the Yokosuka Council on Asia-Pacific Studies.
