  Wilson loop averages are evaluated for large contours and in the large N
limit by means of minimal surfaces. This allows the study of the
quark-antiquark gauge invariant Green function through its dependence on Wilson
loops. A covariant bound state equation is derived which in the center-of-mass
frame and at equal-times takes the form of a Breit-Salpeter type equation. The
interaction potentials reduce in the static case to a confining linear vector
potential. For moving quarks, flux tube like contributions are present. The
nonrelativistic limit is considered.
