The U.S. Department of Energy has asked for more testing on the safety of raising the amount of ethanol allowed in traditional motor fuel above 10 percent, which could delay a decision for months, industry sources said on Thursday.

"DOE is saying the testing isn't done and it may be into the fall before it is done," one of the sources said.

The Environmental Protection Agency had been expected to get the results of the testing later this month and to make a decision on whether to allow levels of up to 15 percent ethanol in traditional gasoline in coming months. The allowable level is currently 10 percent ethanol.

The EPA and DOE did not immediately respond to questions about the matter.