The paper deals with the problem of nonlinear robust stabilization and tracking via state feedback. A robust version of backstepping is designed to control both lateral and rolling motions of a generic air-to-air missile, whose dynamics is highly nonlinear and uncertain. Two kinds of uncertainties are considered: matched and unmatched, whose bounds are assumed to be known a-priori. The nonlinear robust autopilot ensures tracking of sideslip angle reference signal and regulation of bank angle, while maintaining bounded yaw and roll rates. The novelty of the proposed approach relies in a direct compensation of control inputs cross-couplings between lateral and rolling motions, which are generated by differential pressure on the tail-fins.