  Every normal complex surface singularity with $\mathbb Q$-homology sphere
link has a universal abelian cover. It has been conjectured by Neumann and Wahl
that the universal abelian cover of a rational or minimally elliptic
singularity is a complete intersection singularity defined by a system of
``splice diagram equations''. In this paper we introduce a Neumann-Wahl system,
which is an analogue of the system of splice diagram equations, and prove the
following.
  If $(X,o)$ is a rational or minimally elliptic singularity, then its
universal abelian cover $(Y,o)$ is an equisingular deformation of an isolated
complete intersection singularity $(Y_0,o)$ defined by a Neumann-Wahl system.
Furthermore, if $G$ denotes the Galois group of the covering $Y \to X$, then
$G$ also acts on $Y_0$ and $X$ is an equisingular deformation of the quotient
$Y_0/G$.
