When applying an external force to a grafted chain, large configurational transitions may develop depending on the chain's flexibility, its monomer interactions, and the nature of the external bias. We consider the effects of soft stretching on generalized wormlike chains with variable non-bonded pair interactions and persistence length. Force-induced stretching is elicited by periodic perturbations of a terminal bond. We find that flexible chains with strong monomer attractions withstand longer the mechanical stress without undergoing global unfolding. In this case, we observe partly unfolded transients with non-uniform shape features. The relaxation into rod-like conformers depends on the frequency of external stretching. (c) 2005 Elsevier B.V. All rights reserved.