The article is devoted to the regionalization processes in the Asia- Pacific region through the prism of the theory of the formation of mega-regional blocs. In terms of global and regional leadership, this region is becoming a competitive area between two superpowers: the USA and China; this determines the complexity and multiples levels of regional processes, as well as the formation of several regionalization models that run parallel to each other. The purpose of the article is to compare the approaches taken by the United States and China to the formation of mega-regional blocs in the Asia-Pacific region, as well as to outline the ASEAN approach. As a result, the authors conclude that the US approach to the formation of mega-regional blocs is based on more stringent forms of institutionalization, their opposition to the existing system of global trade regulation led by the WTO, and closed principles; the Chinese approach, however, involves combining formal integration with flexible forms of cooperation in certain areas, reliance on the principles of the WTO, and openness to the involvement of new members. The competition between the two superpowers results in fragmentation and sophistication of regionalization trends, and pushes regional actors to search for new forms of strategic collaboration.