Starting from the assumption that the inelastic states in the unitarity relation can effectively be represented by a set of quasi-two-particle states, a K-matrix formalism is set up for high-energy elastic scattering and diffraction-dissociation processes. Using arguments similar to those of Freund, it is shown that the Pomeranchuk contribution to elastic scattering and diffraction dissociation can be generated by multiple exchange of an exchange-degenerate quantum number carrying Regge trajectory R, by considering at the same time a formation of a sequence of excited intermediate states of the colliding particles between the individual R exchanges. This unitarization procedure leads to an imaginary as well as a real contribution for vacuum exchange, corresponding basically to sums of double and triple R-exchange contributions, respectively. At the same time, the K-matrix formalism produces an absorptive correction to the input Born terms. The consequences of the proposed model are worked out, particularly as regards the asymptotic behavior of total cross sections and the interpretation of the crossover phenomenon.