Abstract. An SU (3)-or SU (1, 2)-structure on a 6-dimensional manifold N 6 can be defined as a pair of a 2-form ω and a 3-form ρ. We prove that any analytic SU (3)-or SU (1, 2)-structure on N 6 with dω ∧ ω = 0 can be extended to a parallel Spin(7)-or Spin 0 (3, 4)-structure Φ that is defined on the trivial disc bundle N 6 × Bǫ(0) for a sufficiently small ǫ > 0. Furthermore, we show by an example that Φ is not uniquely determined by (ω, ρ) and discuss if our result can be generalized to nontrivial bundles.