At least one of four states hoping to ease requirements on adding grain-based ethanol to gasoline is expected to petition the federal government as soon as Monday, as the worst drought in 50 years threatens higher corn prices and lowers margins for livestock producers.

Governors from states that may petition the Environmental Protection Agency to waive the mandate known as the Renewable Fuel Standard, or RFS, include Republicans Nikki Haley of South Carolina, Dave Heineman of Nebraska, Rick Perry of Texas, and Democrat Mike Beebe of Arkansas, an ethanol industry source said.

Matt DeCample, a spokesman for Beebe, said the governor is “working on getting the word out to the EPA and others” that the mandate is hurting ranchers and poultry farmers with extra costs, but he has not yet signed on to a specific campaign to petition the agency.