We discuss potential advantages of slow-light waveguides compared to cavity-based structures for enhancing opto-mechanical
interactions. Then, we reveal that slow-light enhanced optical forces between side-coupled photonic-crystal nanowire
waveguides can be flexibly controlled by introducing a relative longitudinal shift. We predict that close to the photonic
band-edge, where the group velocity is reduced, the transverse force can be tuned from repulsive to attractive, and the force
is suppressed for a particular shift value. Additionally the shift leads to symmetry breaking that can facilitate longitudinal
forces acting on the waveguides, in contrast to unshifted structures where such forces vanish.