  We construct a local on-shell invariant in D=11 supergravity from the
nonlocal four-point tree scattering amplitude.Its existence, together with
earlier arguments, implies non-renormalizability of the theory at lowest
possible, two loop, level. This invariant, whose leading bosonic terms are
exhibited, may also express the leading, "zero-slope", M$-$theory corrections
to its D=11 supergravity limit.
