The oil industry is striking back at EPA Administrator Scott Pruitt after he reneged on a proposal to reduce the amount of biofuels blended into the nation's fuel supply.

Oil companies that complain about about the costs of blending ethanol and other biofuels had cheered when Pruitt proposed targets for 2017 and 2018 that are slightly below current levels.

But their feelings changed Friday after Pruitt assured Republican senators in a letter late Thursday night that he would keep the Renewable Fuel Standard levels intact and aim to allow more ethanol to be blended into the gasoline supply year-round.

That promise came amid a major pressure campaign by Midwestern Republicans and Democrats on President Trump and Pruitt to scrap the EPA proposal.

"We are troubled by the departure from accepted law and process that the letter represents," Valero Energy Corp. said Friday.

"These senators have intervened in a regulatory process, and the proposals and concepts in the letter address RFS implementation problems to which these senators have offered no constructive solutions. The only unifying principle of their bullying opposition seems to be a desire to maintain the status quo at all costs and to protect windfall profits associated with unregulated trading of renewable identification numbers, or RINs. Their position advances neither the goals nor the efficient implementation of the RFS, and places U.S. manufacturing jobs at risk."

The Renewable Fuel Standard requirers refiners to blend ethanol or other biofuels into their products or buy credits, known as Renewable Identification Numbers, from refiners that do.

The prices of those credits, which had been stable, have jumped in recent years, which oil refiners say drive up pump prices for consumers.

To respond to those concerns, Pruitt had said he would curtail the program's biofuel targets while allowing ethanol exports to qualify as part of the annual production goals.

But on Thursday, Pruitt changed course and said he would not pursue regulations on the ethanol export idea suggested by refiners.

The ethanol industry sees the idea as detrimental the goal of including more renewable fuels in the nation's fuel supply.

Pruitt's reversal did not settle well with the oil industry.

"The cost to comply with the Renewable Fuel Standard falls disproportionately on the mid-sized refiners and mom-and-pop gas stations that are the backbone of our energy infrastructure," said Greg Blair, spokesman for the Fueling American Jobs Coalition. "If the administration follows the course set out in Administrator Pruitt's letter, manufacturing jobs in Pennsylvania, Ohio and other states – jobs President Trump promised to protect – will be at risk. We hope President Trump doesn't turn his back on American workers."

The EPA must finalize the biofuels regulations by Nov. 30, so it still has time to adjust its plans again.