  The work described in this paper is the first step toward a relativistic
three-quark bound-state calculation using a Hamiltonian consistent with the
Wigner-Bargmann theorem and macroscopic locality. We give an explicit
demonstration that we can solve the two-body problem in momentum space with
spin-dependent interactions. The form of the potential is a combination of
linear+Coulomb+spin-spin+% spin-orbit+tensor, which includes confinement and is
of the general form consistent with rotation, space-reflection and
time-reversal invariance. Comparison is made with previous calculations using
an alternate technique and with the experimental meson mass spectrum. The
results obtained suggest that the model is realistic enough to provide a
two-body basis for the three quark baryon problem in which the Poincar\'{e}
group representation is unitary and cluster separability is respected.
