  The generalization of the effective action [1] of the quark--antiquark system
in the confining vacuum is performed for the case of arbitrary quark masses.
The interaction of quarks is described by the averaged Wilson loop for which we
use the minimal area law asymptotics.
  The system is quantized by the path integral method and the quantum
Hamiltonian is obtained. It contains not only quark degrees of freedom but also
the string energy density.
  As well as in the equal masses case [1] two dynamical regimes are found [2]:
for large orbital excitations ($l \gg 1$) the system is represented as rotating
string, which leads to asymptotically linear Regge trajectories, while at small
$l$ one obtains a potential-like relativistic or nonrelativistic regime.
  In the limiting cases of light-light and heavy-light mesons a unified
description is developed [2]. For the Regge trajectories one obtains nearly
straight-line patterns with the slope very close to $1/2 \pi \sigma$ and $1/
\pi\sigma$ correspondingly. The upper bound on the light quark(s) masses which
doesn't change considerably this property of the trajectories is also found.
