Value iteration in countable state average cost Markov decision processes with unbounded costs

We deal with countable state Markov decision processes with finite action sets and (possibly) unbounded costs. Assuming the existence of an expected average cost optimal stationary policyf, with expected average costg, when canf andg be found using undiscounted value iteration? We give assumptions guaranteeing the convergence of a quantity related tong−Νn(i), whereΝn(i) is the minimum expectedn-stage cost when the process starts in statei. The theory is applied to a queueing system with variable service rates and to a queueing system with variable arrival parameter.