  We consider the change in electron localization due to the presence of
electron-electron repulsion in the \HA model. Taking into account local
Mott-Hubbard physics and static screening of the disorder potential, the system
is mapped onto an effective single-particle Anderson model, which is studied
within the self-consistent theory of electron localization. We find rich
nonmonotonic behavior of the localization length $\xi$ in two-dimensional
systems, including an interaction-induced exponential enhancement of $\xi$ for
small and intermediate disorders although $\xi$ remains finite. In three
dimensions we identify for half filling a Mott-Hubbard-assisted Anderson
localized phase existing between the metallic and the Mott-Hubbard-gapped
phases. For small $U$ there is re-entrant behavior from the Anderson localized
phase to the metallic phase.
