The main goal of this paper is to construct a variant intersectoral dynamic model with planned period and ultimate conditions set endogenously. The construction of this model is made in three stages. At the first stage the basic intersectoral model with the long-term time horizon is constructed. The development of each sector is described in it by the possible variants of creating capacities with its introduction in the certain year of the upcoming perspective. Later allowing for the regime of dynamic planning the groups of sectoral variants are emphasized in the basic model, upon which in the current year of executing calculations, the final decisions should be made. The longitude of the planning period is set so that the capacities of the variants were implemented within its margins. At the second stage, firstly, the terms of constancy in the post-planned period of indicators of input-output on the capacities created in the pre-planned and being created in the planned period are introduced into the basic model and, secondly, the ultimate conditions in the form of functional dependencies of values of input of sectoral capacities in the years of the post-planned period on the sought increases of gross outputs of sectors in the years of the planned period. Such approach to setting the ultimate conditions is called forecasting and optimizing. As a result, the long-term transformed economic model is formed. At the third stage on its base a model of the planned period is constructed. It is proved that the optimal decision of the latter model ensures the achieving of the optimal value of the part of the target function of the transformed long-term model. This part includes only the variables related to the planned period.