  We explore the idea that gravitational interaction can be described by
instantaneous inter-particle potentials. This idea is in full accord with
relativistic quantum theory. In particular, it resembles the ``dressed
particle'' approach to quantum electrodynamics. Although the complete
non-perturbative of this theory is yet unknown, one can reasonably guess its
form in low perturbation orders and in the (1/c)^2 approximation. We suggest a
relativistic energy operator, which in the classical limit reduces to the
Einstein-Infeld-Hoffmann Hamiltonian for massive particles and correctly
describes the effects of gravity on photons, including the light bending, the
Shapiro delay, the gravitational time dilation and the red shift. The causality
of this approach is briefly discussed.
