  The problem of calculating of the mass spectrum of the two-body
Bethe-Salpeter equation is studied with no reduction to the three-dimensional
("quasipotential") equation. The method to find the ground state and excited
states for a channel with any quantum numbers is presented. The problem of the
confining interaction for the Bethe-Salpeter equation is discussed from the
point of view of formal properties of the bound state spectrum, but with only
an inspiration from the QCD. We study the kernel that is non-vanishing at large
Euclidian intervals, $R_E\to \infty$, which is constructed as a special
limiting case of a sum of the covariant one-boson-exchange kernels. When the
usual attractive interaction is added, it is found that this kernel is similar
in its effect to the non-relativistic potential in coordinate space, $V(r)$,
with $V(r\to \infty) \to V_{\infty}$. The positive real constant $V_{\infty}$
gives the scale that define the limit of bound state spectrum compared to the
sum of the constituent masses, $M < 2m + V_{\infty}$. At the same time the
self-energy corrections remove the singularities from the propagators of the
constituents, i.e. constituents do not propagate as free particles. Combination
of these features of the solutions allows an interpretation of this type of
interaction as a confining one. The illustrative calculations are presented for
a model of massive scalar particles with scalar interaction, i.e. the "massive
Wick model".
