Slip-ratio-based controllers are incompetent for precise longitudinal tire force tracking due to non-parametric model uncertainties. The tracking performance further deteriorates whenever the tire is simultaneously accelerating/decelerating and turning. In this paper, we propose an observer-based direct longitudinal tire force control scheme which guarantees achievement of the desired longitudinal tire force robustly with respect to tire model uncertainties, variations in road conditions, and simultaneous lateral tire motions. Convergence of the force estimation/tracking errors is analyzed rigorously by the Lyapunov method. Simulations demonstrate the satisfactory performance on both tire force estimation and tracking.