We derive a formula for the nodal precession frequency and the Keplerian
period of a particle at an arbitrarily inclined orbit (with a minimum
latitudinal angle reached at the orbit) in the post-Newtonian approximation in
the external field of an oblate rotating neutron star (NS). We also derive
formulas for the nodal precession and periastron rotation frequencies of
slightly inclined low-eccentricity orbits in the field of a rapidly rotating NS
in the form of asymptotic expansions whose first terms are given by the
Okazaki--Kato formulas. The NS gravitational field is described by the exact
solution of the Einstein equation that includes the NS quadrupole moment
induced by rapid rotation. Convenient asymptotic formulas are given for the
metric coefficients of the corresponding space-time in the form of Kerr metric
perturbations in Boyer--Lindquist coordinates.Comment: 12 page
