The Environmental Protection Agency quietly announced on Friday that, after much delay, it had been unable to decide this year on a rule setting levels for the amount of biofuel it would require to be blended into conventional vehicle fuels.

Because of the delay, a spokeswoman said in a statement, the agency will not take up the rule, known as the Renewable Fuel Standard, until next year, when it seeks to set levels for 2015 and 2016.

A notice posted on the E.P.A. website said that the agency’s proposal, released last year, to reduce biofuel targets had “generated significant comment and controversy,” especially over how the biofuel targets should be set and whether it would be effective in, “achieving the volumes of renewable fuel targeted by the statute.” Given continued consideration of those issues, the notice said, the agency would not reach a decision this year.

The notice also said the agency would adjust reporting requirements so refiners could comply retroactively.