  We construct power series invariants of rational homology 3-spheres from
quantum PSU(n)-invariants. The power series can be regarded as perturbative
invariants corresponding to the contribution of the trivial connection in the
hypothetical Witten's integral. This generalizes a result of Ohtsuki (the $n=2$
case) which led him to the definition of finite type invariants of 3-manifolds.
The proof utilizes some symmetry properties of quantum invariants (of links)
derived from the theory of affine Lie algebras and the theory of the Kontsevich
integral.
