TOKYO—The Bank of Japan must maintain ultra-loose monetary policy as recent cost-push inflation could hurt the economy, Governor Haruhiko Kuroda said on Tuesday, highlighting a widening gap with the U.S. Federal Reserve’s aggressive tightening plan. The central bank’s increasingly isolated dovish stance helped push the yen below 120 to the dollar on Tuesday for the first time since 2016, drawing a warning from the finance minister against rapid exchange-rate moves. Kuroda said consumer inflation was expected to accelerate as some firms pass on rising energy and food costs to households. “Instead of leading to higher wages and corporate profits, such cost-push inflation will weigh on the economy in the long run by hurting corporate profits and households’ real income,” Kuroda told parliament. While nominal wages may increase “quite significantly,” the rise in consumer inflation may sap households’ purchasing power by pushing down price-adjusted real wages, he added. “Given recent price …