A mechanism for fueling active galactic nuclei and nuclear starburst galaxies is suggested. It consists of two stages. First, a large-scale stellar bar sweeps the ISM into a gaseous disk of a few hundred pc radius. This disk may, under certain conditions, become dynamically unstable, induce radial flow, and feed viscosity-driven accretion flow around a black hole. It may lead to the formation of a black hole if none was present initially.