Target tracking using Wireless Sensor Networks (WSNs) is a widely studied application area. However, the available power at each sensor node and the energy required to transmit the sensed information to a network sink have limited the use of WSNs in target tracking applications. In this paper, the use of a mobile robot, working in conjunction with the WSN, to track a target is studied. The trilateration approach is used to detect the presence of the target and a Kalman Filter is used to estimate its location. An algorithm is proposed that enables the selection of a minimum number of sensor nodes to track the target and to determine the path of the mobile robot for efficient tracking. Theoretical proofs are developed to mathematically demonstrate the convergence of the target tracking algorithm.