While the United States has turned a new page in its relations with former adversary Vietnam, cracks in ties with long-standing allies the Philippines and Thailand present challenges for its foreign policy in Southeast Asia. The bid to strengthen its historical alliances in the region – and win a new partner – will test Washington’s ability to sustain its post-war hub-and-spokes system of influence while trying to enlarge it against the backdrop of China’s growing economic and political clout. On his trip to Southeast Asia earlier this month, US Defence Secretary Mark Esper reassured allies and partners about Washington’s commitment to the region while he tried to roll back Chinese influence . The trip was the second multi-country visit he had made to the region in the past three months, signalling its strategic importance to the American concept of a free and open Indo-Pacific. Washington’s response to an array of challenges in Southeast Asia, from the South China Sea to its rivalry with China, may determine the US’ role in a mega-region it considers most consequential for its future. As US-China rivalry intensifies, smaller states in Southeast Asia seek a way to thrive When it comes to establishing a new regional partner, American relations with its former cold war nemesis Vietnam surprisingly hold the most promise. From security and energy to aviation, bilateral ties show encouraging gains, although problems persist. In Hanoi, Esper met Prime Minister Nguyen Xuan Phuc, defence minister Ngo Xuan Lich, and Tran Quoc Vuong, the executive secretary of the Communist Party. This high-level welcome speaks of the tremendous turnaround in relations in recent years, marked by the lifting of the arms embargo in 2016 and the visit of aircraft carrier USS Carl Vinson last year. In a speech at the Diplomatic Academy of Vietnam, Esper used story written by Greek historian Thucydides – in which Athens, a naval power, used the logic of “might is right” to subjugate the independent island of Melos – as an analogy for China’s actions in the South China Sea. Aside from getting vocal US support against Chinese interference in Vietnam’s oil and gas activities, Hanoi will also receive a second Hamilton-class endurance cutter. In early November, commerce secretary Wilbur Ross led a trade mission to the Vietnamese capital, which saw several billion-dollar deals struck. These include an offshore oil production-sharing contract between American firm Murphy Oil, South Korean firm SK Innovation and state-owned PetroVietnam. AES Corporation, another US company, signed a deal to build a gas-fired power plant connected to a liquefied natural gas terminal. This infrastructure can diversify Vietnam’s sources of imported energy, boosted by the US’ re-emergence last year as the world’s largest producer of oil and gas. But while trade relations have vastly improved and the US has become Vietnam’s largest export market, the growing trade deficit and Hanoi’s alleged currency devaluation have seen Washington label the country as a currency manipulator and threaten it with sanctions. Manila must play its cards right with Chinese offshore gambling Esper’s trip also took him to Thailand, where he joined his regional counterparts for the Asean Defence Ministers Meeting-Plus. The US will not find it easy to roll back Chinese influence in the kingdom, as this clout has gained much headway since the 2014 military coup. Fortuitously, the normalisation of relations between Bangkok and Washington – which began with the visit of General Prayuth Chan-ocha to the American capital in 2017 – continues, despite US accusations of electoral fraud in Thailand’s March elections. The US curbed military aid to Thailand following the 2014 coup, but its decision to lift these restrictions has allowed the Southeast Asian nation to procure American-made Stryker armoured personnel carriers (APCs), the first batch of which arrived in September. But American defence contractors have some catching up to do, as China has this year already bagged deals to sell Thailand a broad range of arms platforms including a huge amphibious vessel, APCs, tanks and potentially a second submarine next year. Esper’s former hat as a corporate lobbyist for US defence contractor Raytheon may be helpful in this regard. In addition, President Donald Trump’s nomination of lawyer Michael DeSombre, worldwide president of Republicans Overseas, as the next ambassador to Thailand may also send unwanted signals. DeSombre would become the first political appointee – as opposed to a career diplomat – to serve the Bangkok post since 1975. The appointment may be taken as diminishing the importance Washington attaches to the first Asian country with which it entered formal diplomatic relations, as far back as 1833. Moreover, as China looks to secure naval and air facilities in neighbouring Cambodia, securing a foothold in Thailand is important for the US. In the Philippines, the challenge the US faces is to impress the enduring value of its alliance as Manila forges closer ties with Beijing and Moscow, as well as to allay doubts about the 1951 Mutual Defence Treaty’s capacity to handle new security challenges. Chinese fishing vessels in South China Sea might net more than they bargained for Esper’s trip saw him meet his Filipino counterpart Delfin Lorenzana, with the two reiterating the treaty’s relevance when it came to the issue of Philippine sovereign rights in the South China Sea. In their joint statement, the two defence chiefs also committed to support the modernisation of the Philippines’ military, particularly its maritime and aerospace capabilities. While Lorenzana’s calls to review the treaty have yet to be addressed, the clarification of its scope assuaged concerns about US readiness to respond should Manila come under attack in the disputed waterway. In the meantime, the existing bilateral Mutual Defence Board-Security Engagement Board serves as the venue for Washington and Manila to discuss traditional and non-traditional security threats. To the US’ relief, Lorenzana continues to champion the long-standing bilateral defence ties. While Philippine President Rodrigo Duterte is already on his third foreign affairs secretary, Lorenzana – a former defence attaché to the US – remains a steady hand in the cabinet. Close to 30 years since the end of the cold war, allies and partners remain critical to Washington’s projection of power and global leadership. In the age of competition between great powers, these allies have become indispensable. But as they grow from proxies to become sovereign actors with full agency and varied interests, dealing with them requires skill and foresight. Lucio Blanco Pitlo III is a research fellow at the Asia-Pacific Pathways to Progress Foundation. He is an analyst on Asian connectivity and security affairs and is presently pursuing his MA International Affairs at American University in Washington.