We introduce the possibility of trade in dynamic models with externalities and evaluate the consequences on the capital accumulation process, the market-clearing prices and policy making. We consider mixed economies characterized by a blend of strategic and nonstrategic sectors. An equilibrium exists in the bilateral monopoly game because the strategic planner incorporates the future utility of the country and the presence of a nonstrategic sector in its decision making. Capital externality is one source of interdependence. Equilibrium price, a function of both outputs, is another. Policy coordination is advantageous only when preferences are dissimilar and an externality is present.