Embedded agents deployed in physical environments are increasingly interoperable, and are likely to coexist with agents of others systems in a same physical space. So, an agent needs to be able to cooperate with agents from other systems and to form coalitions with unfamiliar teammates. However, before committing to cooperate with others, an agent must take into account that it may get involved in the achievement of objectives that are incompatible with its own, with the global objectives of its system, or with those derived from its previously joined coalitions. To avoid such situations, we propose an identity-based cooperation mechanism. This mechanism involves creating and sustaining the agent identity, and a commitment process to reason about identities when solicited to participate in a collective trans-MAS action.