This paper presents an integrated task planning and control approach for manipulating a nonholonomic cart by mobile manipulators. The task considered in this study is to manipulate a nonholonomic cart to perform certain tasks such as pushing the cart along a straight line, making a turn at a corner, or tracking a sine wave. The cart manipulation task fully integrates the motion and force planning of the cart, and the planning and control of the mobile manipulators. The motion of the mobile manipulator and cart is coordinated by a common motion reference. The cart manipulating control has been implemented based on the decoupled mobile manipulation model and the force planning of the cart. The proposed integrated task planning and control approach enables the mobile manipulator complete complicated tasks by regulating its output force. The approach has been tested on a mobile manipulator consisting of a Nomadic XR4000 and a Puma 560 robot arm. The experimental results demonstrate the efficacy of this approach in the mobile manipulation of a nonholonomic cart.