  We employ the $\Phi-$ derivable approach to many particle systems with strong
correlations that can lead to the formation of bound states (clusters) of
different size. We define a generic form of $\Phi-$ functionals that is fully
equivalent to a selfconsistent cluster virial expansion up to the second virial
coefficient for interactions among the clusters. As examples we consider nuclei
in nuclear matter and hadrons in quark matter, with particular attention to the
case of the deuterons in nuclear matter and mesons in quark matter. We derive a
generalized Beth-Uhlenbeck equation of state, where the quasiparticle virial
expansion is extended to include arbitrary clusters. The approach is applicable
to nonrelativistic potential models of nuclear matter as well as to
relativistic field theoretic models of quark matter. It is particularly suited
for a description of cluster formation and dissociation in hot, dense matter.
