for instance tier one in the euunited states proposal covers energyrelated services eg engineering and maintenance services to optimize the environmental performance of energy facilities and services for the design and construction of energyefficient buildings and facilities tier two covers a broad set of environmental and climaterelated services including energy construction architectural engineering and integrated engineering services once the picture on the services front is sufficiently clear the negotiators would proceed to identify the goods essential to the delivery of the selected environmental and energy services and negotiate tariff concessions using the proposed modalities and taking into account national priorities and programmes the introduction of sustainability standards and regulations may prove important to trade in biofuels