  We present an analytical description of top-antitop pair production near the
threshold in $e^+e^-$ annihilation and $\g\g$ collisions. A set of basic
observables considered includes the total cross sections, forward-backward
asymmetry and top quark polarization. The threshold effects relevant for the
basic observables are described by three universal functions related to S wave
production, P wave production and S-P interference. These functions are
computed analytically up to the next-to-next-to-leading order of NRQCD. The
total $e^+e^-\to t\bar t$ cross section near the threshold is obtained in the
next-to-next-to-leading order in the closed form including the contribution due
to the axial coupling of top quark and mediated by the Z-boson. The effects of
the running of the strong coupling constant and of the finite top quark width
are taken into account analytically for the P wave production and S-P wave
interference.
