This paper describes a sensor-based robot control method for handling non contact to contact transitions in partially unknown environment. The proposed approach is based on the integration of proximity and force/torque sensing capabilities. Proximity information is used not only to avoid undesired contacts during robot operation but also to improve efficiency in terms of speed and safety, when the contact is desired. By detecting in advance the target surface to be reached, it is possible to plan the trajectory in order to optimize the approach velocity profile, as well as to maintain the impact forces at the desired level by means of force control.