Résumé : This article draws the attention firstly on the diffusion of macro-regional organizations in each continent as well as on the inter-regional relations. Secondly it places this intermediary levels of governance - between states and global organizations - in the context of the big challenge of the interpretation of the current global order change after 1991. On the basis of a sophisticated conceptualization of both regionalism and inter-regionalism the articles addresses the impact of the multipolar power structure of the world, on regional cooperation. Two alternative scenarios are forecasted as outcome of this comparative research: either an instrumental and authoritarian downgrading of regional cooperation as influence spheres of great powers or the gradual emergence of a new multilateralism, post-hegemonic multilayered, more legitimate and more efficient.