  We construct a set of 2^(2^n) independent Bell correlation inequalities for
n-partite systems with two dichotomic observables each, which is complete in
the sense that the inequalities are satisfied if and only if the correlations
considered allow a local classical model. All these inequalities can be
summarized in a single, albeit non-linear inequality. We show that quantum
correlations satisfy this condition provided the state has positive partial
transpose with respect to any grouping of the n systems into two subsystems. We
also provide an efficient algorithm for finding the maximal quantum mechanical
violation of each inequality, and show that the maximum is always attained for
the generalized GHZ state.
