The ASEAN Plus Three (APT) framework, comprising the ten member states of ASEAN and China, Japan, and South Korea, was established in 1997 amidst the Asian Financial Crisis. Its primary objective was to foster closer cooperation and address regional challenges, particularly in economic and financial stability, but also extending to political-security and socio-cultural domains. Overall, the APT has demonstrated considerable success in enhancing regional cooperation and dialogue, though its effectiveness can vary depending on the specific issue.

In the economic and financial sphere, the APT has been particularly successful. A key achievement is the Chiang Mai Initiative Multilateralisation (CMIM), a multilateral currency swap arrangement designed to provide financial support to member countries facing short-term liquidity problems. This mechanism, with its substantial fund, serves as a crucial regional safety net, preventing a recurrence of the 1997 crisis. Furthermore, the APT has promoted trade and investment through various initiatives, including discussions on regional free trade agreements and enhancing supply chain resilience. The ASEAN+3 Emergency Rice Reserve (APTERR) is another tangible example, established to ensure food security in the region by providing emergency rice stocks during natural disasters or food shortages.

In addressing non-traditional security threats, the APT has facilitated cooperation on issues like disaster management, counter-terrorism, and public health. Following outbreaks like SARS and H1N1, the APT countries enhanced collaboration on disease surveillance, prevention, and control, sharing best practices and resources. Regular ministerial meetings and senior officials' consultations across various sectors, including finance, agriculture, tourism, and environment, have created robust platforms for dialogue and coordination.

However, the APT's success in addressing more contentious political-security problems, such as territorial disputes in the South China Sea, has been more limited. While it provides a forum for discussion, the framework often struggles to move beyond consensus-based statements to concrete actions when major power interests diverge. The inherent competition among the 'Plus Three' countries, particularly between China and Japan/South Korea, can also sometimes impede deeper integration and collective problem-solving.

Despite these limitations, the APT remains a vital component of the East Asian regional architecture. It has successfully institutionalized dialogue, fostered economic interdependence, and built a degree of trust among diverse nations. Its ability to provide a platform for major regional powers to engage with ASEAN centrality, while addressing common challenges, underscores its significant, albeit evolving, success.