  Presently the quarkonium spectrum, written in terms of the quark MSbar-mass,
is known at O(alpha_s^3 m) accuracy. We point out that in order to achieve
O(alpha_s^4 m) accuracy it is sufficient to calculate further (I) the
O(alpha_s^4 m) relation between the MSbar-mass and the pole-mass, and (II) the
binding energy at O(alpha_s^5 m) in the large-beta_0 approximation. We
calculate the latter correction analytically for the 1S-state and study its
phenomenological implications.
