We address the problem of the automated verification of temporal properties of infinite state reactive systems. We present some improvements of a verification method based on the specialization of constraint logic programs (CLP). First, we reformulate the verification method as a two-phase procedure: (1) in the first phase a CLP specification of an infinite state system is specialized with respect to the initial state of the system and the temporal property to be verified, and (2) in the second phase the specialized program is evaluated by using a bottom-up strategy. In this paper we propose some new strategies for performing program specialization during the first phase. We evaluate the effectiveness of these new strategies, as well as tha...