  Starting from the effective lagrangian for QCD at high energy we calculate
the lowest perturbative contributions to the potential of a relativistic
nucleus and compare our results to those derived by Kovchegov (see Y.V.
Kovchegov, Phys. Rev. {\bf D55}, 5445 (1997)). The results differ already at
order g^3 which can be traced to the fact that the meaning of the underlying
gluon fields is different. (The effective gluon field we use is a gauge
invariant object.) Both approaches should therefore be seen as alternatives,
the relative merits of which have to be judged by their phenomenological
success.
