The article focuses on the research of the policy of Japan and China in Southeast Asia at the present stage. The paper analyses the process of establishment and subsequent development of the ''ASEAN Plus Three'' (APT) framework, which includes ten countries of ASEAN and three Northeast Asian states of China, Japan and South Korea. ''ASEAN Plus Three'' might serve as catalyst for the processes of economic and political integration in East Asia. The rivalry of China and Japan is a major constraint to the development of integration structures. How can we characterize the existing relations between Japan and China? Who are they partners or competitors? From the economic point of view the development of the economies of Japan and China in recent decades has been more complementary than competitive. As for political relations these largest Asian countries have always been and will likely be irreconcilable antagonists. Cooperation and competition of China and Japan have an increasing influence on world politics and economy. On the one hand, these countries are each other's important resource for economic growth, and steadily growing economic interdependence compels them to seek new ways of mutually beneficial cooperation. On the other hand, China and Japan are competing not only in the struggle for access to new sources of energy, but also for leadership in the geopolitical space of East Asia. In recent years the Chinese government has actively pursued a policy of strengthening cooperation with different regional integration structures. Cooperation between China and ASEAN, the leading organization in Southeast Asia, has intensified significantly. It is important to note that cooperation of China and ASEAN to some extent seems paradoxical, since their competition in export markets is much higher than the competition between Japanese and Chinese goods. The rapid growth of Chinese economy is perceived rather ambiguously. China's economic growth produces a double effect on its neighbours. It attracts them, potentially ensuring economic growth, but at the same time, is disturbing. It is clear that Chinese government would not miss an opportunity to press its geopolitical rivals in Southeast and East Asia and finally consolidate the leading position in the region. Our analysis suggests that the regional leader in East and Southeast Asia at the moment is China.
