We numerically study the dependence of the dynamics on the range of interaction Δ for the short-range square well potential. We find that, for small Δ, dynamics scale exactly in the same way as thermodynamics, both for Newtonian and Brownian microscopic dynamics. For interaction ranges from a few percent down to the Baxter limit, the relative location of the attractive-glass line and the liquid-gas line does not depend on Δ. This proves that, in this class of potentials, disordered arrested states (gels) can be generated only as a result of a kinetically arrested phase separation. © 2005 The American Physical Society.