Many answer set solvers utilize Satisfiability solvers for search. SMT solvers extend Satisfiability solvers. This paper presents the CMODELS-DIFF system that uses SMT solvers to find answer sets of a logic program. Its theoretical foundation is based on Niemala's characterization of answer sets of a logic program via so called level rankings. The comparative experimental analysis demonstrates that CMODELS-DIFF is a viable answer set solver.