  A 7-manifold with G_2 holonomy can be constructed as a R^3 bundle over a
quaternionic space. We consider a quaternionic base space which is singular and
its metric depends on three parameters, where one of them corresponds to an
interpolation between S^4 and CP^2 or its non-compact analogs. This 4-d
Einstein space has four isometries and the fixed point set of a generic Killing
vector is discussed. When embedded into M-theory the compactification over a
given Killing vector gives intersecting 6-branes as IIA configuration and we
argue that membrane instantons may resolve the curvature singularity.
