[en] A redefined version of Hartle's perturbative method of solving Einstein's equations for rotating massive objects is applied for the investigation of the general relativistic Kepler frequency of a rotating neutron star. From the precise determination of rotating limiting mass neutron star models for seventeen representative neutron matter equations of state we find Kepler frequencies which are systematically larger by ≅(10-15)% than those obtained from the empirical formula of Haensel and Zdunik. The latter results however can be reproduced from Hartle's method as well by accounting for a small mass uncertainty of the limiting star model of < or approx.2%. In comparison with an exact numerical solution, Hartle's method is relatively easy to implement and should prove to be a practical tool for testing the compatibility of nuclear equations of state on pulsar periods. (orig.)