A method of iterative negotiation for improved production planning between one or more purchasers and suppliers in a supply chain. The method includes a purchaser in a supply chain generating a request schedule that is communicated to a supplier. In response to the request schedule the supplier generates a commit schedule and communicates it back to the purchaser. Through the iterative negotiation process (ask-answer) one or more interpolation constraints are generated based on the supplier's commit schedules. Upon completion of the ask-answer process purchaser solves a final advanced planning system (APS) based on said one or more interpolation constraints and generates a final production plan. The invention can be employed to integrate the collaboration among purchasers and suppliers with an advanced planning system for optimizing established planning objectives (e.g. customer service, short lead times, low inventory, and prioritized allocation of supply and capacity).