  We obtain an estimate for the norm of the second fundamental form of stable
H-surfaces in Riemannian 3-manifolds with bounded sectional curvature. Our
estimate depends on the distance to the boundary of the surface and on the
bounds on the geometry of the ambient manifold but not on the manifold itself.
We give some applications, in particular we obtain an interior gradient
estimate for H-sections in Killing submersions.
