The idea of “AUKUS Plus” has reemerged after the U.K. Foreign Affairs Committee issued a 2023 report saying the United Kingdom should extend cooperation “to partners such as Japan and South Korea” as part of AUKUS “Strand B” — or “Pillar Two.” This strand focuses on military technology cooperation with close allies on cyber warfare, artificial intelligence, quantum and undersea innovations, hypersonics and counter-hypersonics, electronic warfare capabilities and further information sharing.
While “Pillar One” — which is concerned with nuclear-powered submarine building — remains exclusive to AUKUS’ core of Australia, United Kingdom and the United States, the possibility of Pillar Two cooperation has opened public discussion about partnership enlargement. Neither such cooperation nor enlargement will materialize anytime soon unless there is an abrupt shift in the Indo-Pacific’s balance of power.
Still, the United Kingdom’s statement illustrates the evolution of its Indo-Pacific strategy “Tilt.” Tilt indicates the United Kingdom’s renewed commitment to the Indo-Pacific, and its aim to garner regional support for U.K. involvement and to shape a regional balance of power in its favor. More importantly, this move plays a role in shaping the direction of regional coalition-building efforts.
The United Kingdom understands that the possibility of AUKUS membership expansion is still in its initial stages, with the report recommending that the U.K. government “[propose]” the idea to the United States and Australia. There are challenges to overcome before the proposal is considered seriously among the core three.
There is yet to be consensus about the expansion. Australia, the initiator of the security coalition, has previously alluded to membership expansion in Pillar Two, but eventually dismissed the idea. Former Australian prime minister Scott Morrison stated in March 2023 that the inclusion of Japan would be “premature” and that AUKUS should prioritize institutional consolidation.
For his part, U.S. National Security Council Coordinator for the Indo-Pacific Kurt Campbell touched on the idea of including other countries in Pillar Two of AUKUS. Yet he remained ambiguous about timing and stated that it should be done under the condition that a potential member shows a substantive contribution to AUKUS.
It is still not clear whether AUKUS is the best platform to expand cooperation with Japan, South Korea and others. The United States, Japan and South Korea have gained political momentum and further strengthened their trilateral cooperation, as illustrated in the 2023 joint statement “The Spirit of Camp David.” Their strategic cooperation now includes supply chain resilience, artificial intelligence and quantum computing — which resonates with Pillar Two of AUKUS.
Given the existence of these platforms, there is no real urgency for AUKUS and the U.S.-Japan-South Korea trilateral cooperation to converge. For now, the United States is well-positioned to become a hub to coordinate the two trilateral frameworks and guide them towards future cooperation.
The expansion of AUKUS might be perceived as a unified diplomatic front against China. Of course, there is no question that the United States, Australia and the United Kingdom have taken a firm stance against China’s assertive behavior in the Indo-Pacific region and its threat to the existing international order.
Japan remains cautious but has clearly expressed serious concerns about China’s strategic posture, which it considers “unprecedented and the greatest strategic challenge” to its security and the existing international order. South Korea, under the Yoon administration, has also shown its strategic interest in engaging with AUKUS. Hence, the creation of AUKUS Plus is gaining diplomatic momentum.
That said, Japan and South Korea, being geographically close to and having substantial economic interactions with China, need to carefully manage their relationship with AUKUS. At least in the short term, they must provide a convincing rationale for any shifts toward AUKUS to avoid unnecessarily deteriorating their relations with China.
A history of recurring remarks pushing for AUKUS membership expansion suggests that, regardless of the United Kingdom’s strategic intentions, these statements function as a foreign policy signal for coalition-building. For example, there were domestic political changes in South Korea in 2022 and such statements allowed AUKUS members to gauge South Korea’s new strategic posture.
The statements can check for any changes in member states’ political desire for the creation of AUKUS Plus. This is particularly helpful since the strategic landscape in the Indo-Pacific region and beyond continues to evolve. The United States and the United Kingdom are distracted because of existing and emerging regional crises, such as in Ukraine and Israel. These may push them to facilitate larger coalition-building efforts.
Such statements stir public discourse within and outside the three core members, shedding light on various country-specific perspectives on AUKUS, including its benefits, costs and concerns. Japan has expressed interest in joining AUKUS Pillar Two efforts, yet any collaboration over nuclear-powered submarines would likely face public pushback because of sensitivities to nuclear-related norms.
In the rapidly changing global strategic environment, coalition-building is the key to shaping the existing and emerging regional order. This process takes a long time and foreign policy signaling becomes imperative in policy coordination and strategic collaboration. In this context, the United Kingdom’s proposal to partner with other nations should be encouraged in the future.
Kei Koga is Head of Public Policy and Global Affairs Program and Associate Professor at the School of Social Sciences, Nanyang Technological University, Singapore.