The Reserve Bank of New Zealand is expected to keep its key policy rate unchanged on Wednesday but a slim majority of economists in a Reuters poll now forecast one or more hikes by end-September as a global energy shock threatens to lift inflation expectations. All but one of 29 economists surveyed May 18-22 expected policymakers to hold the official cash rate at 2.25% on May 27. Just over half, nearly 52%, predicted one or two rate hikes by the end of the third quarter.