  We estimate the QCD effective charge $\alpha_s$ in the low-energy region by
exploiting the conventional meson spectrum within a relativistic quantum-field
model based on analytic confinement. The ladder Bethe-Salpeter equation is
solved for the masses of two-quark bound states. We found a new, independent
and specific infrared-finite behavior of QCD coupling below energy scale 1 GeV.
Particularly, an infrared-fixed point is extracted at $\alpha_s(0)\simeq 0.757$
for confinement scale $\Lambda=345$ MeV. As an application, we estimate masses
of some intermediate and heavy mesons and obtain results in reasonable
agreement with recent experimental data.
