The U.S. Environmental Protection Agency, which was expected to decide this month whether American car engines can handle higher concentrations of ethanol in gasoline, has postponed the decision until at least September. The agency had been expected to decide by this month whether to increase the maximum blend from 10 to 15 percent. The EPA said Thursday that initial tests on a 15-percent blend, up from 10 percent, "look good" and should be completed by the end of September. A decision will come after the Energy Department completes the testing of the higher blend on vehicles built after 2007. The EPA has indicated in the past that it will raise the blend, saying a congressional mandate for increased ethanol use can't be achieved without allowing higher blends of the renewable fuel, most of which comes from corn despite overwhelming evidence than corn ethanol is bad for the planet. Congress has required refiners to blend 12.9 billion gallons of biofuels in 2010, of which 12 billion gallons would be ethanol. The mandate soars to 36 billion gallons, mostly ethanol, by 2022. This is the second time the EPA has announced a delay of its decision on the blend. The agency pushed the decision to June last December, saying further testing was needed.