Reduction of the QCD string to a time component vector potential

We demonstrate the equivalence of the relativistic flux tube model of mesons to a simple potential model in the regime of large radial excitation. We make no restriction on the quark masses; either quark may have a zero or finite mass. Our primary result shows that for fixed angular momentum and large radial excitation, the flux tube or QCD string meson with a short-range Coulomb interaction is described by a spinless Salpeter equation with a time component vector potential V(r)=ar-k/r.