Extending the applicability of reachability analysis to large and real circuits is a key issue. In fact they are still limited for the following reasons: peak BDD size during image computation, BDD explosion for representing state sets and very high sequential depth. Following the promising trend of partitioning and problem decomposition, we present a new approach based on a disjunctive partitioned t r ansition relation and on an improved iterative squaring. In this approach a Finite State

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... ne is decomposed and traversed one \functioning{mode" at a time by means of the \disjunctive" partitioned approach. The overall algorithm aims at lowering the intermediate peak BDD size pushing further reachability analysis. Experiments on a few industrial circuits containing counters and on some large benchmarks show the feasibility of the approach.