We present a new stabilization approach for a linear plant with input delay, parametric
uncertainties, and an unknown harmonic disturbance. To solve this problem, we combine
the well-known predictor feedback approach with the state observer and adaptive scheme
that identifies the frequency of the disturbance. Compared to the existing approaches, the
dynamic order of our adaptive scheme is low (equal to three) and the results apply to plants
that are unstable, non-minimum phase, and have an arbitrary relative degree.