  We calculate a large $k$ asymptotic expansion of the exact surgery formula
for Witten's $SU(2)$ invariant of Seifert manifolds. The contributions of all
flat connections are identified. An agreement with the 1-loop formula is
checked. A contribution of the irreducible connections appears to contain only
a finite number of terms in the asymptotic series. A 2-loop correction to the
contribution of the trivial connection is found to be proportional to Casson's
invariant.
