  We derive the complete set of velocity-enhanced terms in the expansion of the
total cross section for heavy-quark pair production in hadronic collisions at
next-to-next-to-leading order. Our expression takes into account the effects of
soft-gluon emission as well as that of potential-gluon exchanges. We prove that
there are no enhancements due to subleading soft-gluon couplings multiplying
the leading Coulomb singularity.
