Abstract
The destruction of quantum localization of chaos by weak nonlinearity is analyzed on the basis of the Chirikov criterion of overlapping resonances. It is shown that for the nonlinear coupling constant there is a delocalization border above which localization is destroyed. In this delocalized phase, excitation is described by a universal anomalous subdiffusion law. Applications of this phenomenon to nonlinear wave propagation in disordered media and Anderson localization are discussed.