Coordination of two manipulators performing the task of transporting objects is studied in this paper. Each manipulator is equipped with end effector - a flat surface palm. Grasping is achieved by the two palms pushing an object from two ends. The task requires simultaneous control of the object motion and the interaction force. The control of the interaction force is needed to ensure that the object is not dropped and to avoid excessive pressing. The motion and force control problem is further complicated by the presence of unilateral constraints since the manipulators can only push the object. This paper describes a control method which utilizes a state feedback to decouple position control and force control loops. A force control planning algorithm is also proposed which ensures the satisfaction of unilateral constraints. The effectiveness of the control method is verified by simulations.