  We compare the physical potential $V_D(R)$ of an external quark-antiquark
pair in the representation $D$ of SU(N), to the color-Coulomb potential $V_{\rm
coul}(R)$ which is the instantaneous part of the 44-component of the gluon
propagator in Coulomb gauge, $D_{44}(\vx,t) = V_{\rm coul}(|\vx|) \delta(t)$ +
(non-instantaneous). We show that if $V_D(R)$ is confining, $\lim_{R \to
\infty}V_D(R) = + \infty$, then the inequality $V_D(R) \leq - C_D V_{\rm
coul}(R)$ holds asymptotically at large $R$, where $C_D > 0$ is the Casimir in
the representation $D$. This implies that $ - V_{\rm coul}(R)$ is also
confining.
