MENLO, Iowa (AP) — With inflation at a 40-year high, President Joe Biden journeyed to corn-rich Iowa on Tuesday to announce a modest step aimed at trimming gasoline prices by about a dime a gallon at a limited number of stations by waiving rules that restrict ethanol blending.

His action reflects the ways Biden is deploying almost every weapon in his bureaucratic arsenal to ease price pressures, yet the impact appears to be small and uncertain. Inflation has only accelerated in recent months, instead of fading as Biden once promised it would after the recovery from the coronavirus recession fo...