  Let (M,g_0) be a compact Riemannian manifold of dimension n \geq 4. We show
that the normalized Ricci flow deforms g_0 to a constant curvature metric
provided that (M,g_0) x R has positive isotropic curvature. This condition is
stronger than 2-positive flag curvature but weaker than 2-positive curvature
operator.
