[en] Deep inelastic e^-p scattering has been studied in both the charged current (CC) and neutral current (NC) reactions at momentum transfers squared, Q², between 400 GeV² and the kinematic limit of 87500 GeV² using the ZEUS detector at the HERA ep collider. The CC and NC total cross sections, the NC to CC cross section ratio, and the differential cross sections, dσ/dQ², are presented. For Q²∝M_W², where M_W is the mass of the W boson, the CC and NC cross sections have comparable magnitudes, demonstrating the equal strengths of the weak and electromagnetic interactions at high Q². The Q² dependence of the CC cross section determines the mass term in the CC propagator to be M_W=76±16±13 GeV. (orig.)