Renormalization-group improved calculation of top-quark production near threshold

The top-quark cross section close to threshold in e(+)e(-) annihilation is computed including the summation of logarithms of the velocity at next-to-n ext-to-leading-logarithmic order in QCD. The remaining theoretical uncertai nty in the normalization of the total cross section is at the few-percent l evel, an order of magnitude smaller than in previous next-to-next-to-leadin g order calculations. This uncertainty is smaller than the effects of a lig ht standard-model Higgs boson.