WASHINGTON (Reuters) - Five Republican senators are warning President Donald Trump’s new pick to run the Environmental Protection Agency, Andrew Wheeler, that their support for his nomination may hinge on his biofuels policy.

FILE PHOTO: Acting Administrator of the Environmental Protection Agency Andrew Wheeler speaks during an event hosted by U.S. President Donald Trump with workers on "Cutting the Red Tape, Unleashing Economic Freedom" in the Oval Office of the White House in Washington, U.S., October 17, 2018. REUTERS/Joshua Roberts/File Photo

The senators, all from states hosting oil refineries, said they want to be assured that Wheeler would work to reduce the regulatory costs for oil companies of complying with the U.S. Renewable Fuel Standard before they decide on whether to back him as permanent chief of the EPA.

The Renewable Fuel Standard requires oil refiners to blend increasing amounts of biofuels like corn-based ethanol into their fuel each year, or purchase blending credits from those who do. The measure is intended to help farmers and reduce U.S. dependence on foreign energy sources, but oil refining companies - like Valero Energy Corp and billionaire investor Carl Icahn’s CVR Energy Inc - complain it costs them a fortune.

“Without an adequate proposal to meaningfully lower the regulatory burden ... we will have serious concerns with your nomination,” the five Republican senators said in a letter to Wheeler dated Feb. 11.

The letter was signed by Ted Cruz of Texas, Pat Toomey of Pennsylvania, Michael Lee of Utah, as well as both John Kennedy and Bill Cassidy of Louisiana.

The five were due to meet with Wheeler later on Wednesday night to discuss biofuels, according to two sources familiar with the matter.

The EPA is working on a number of critical adjustments to its biofuel policy that are of interest to the oil industry, including resetting targets for annual biofuels blending volumes, lifting a summertime ban on higher-ethanol blends of gasoline, and proposing measures to limit speculation in the blending credit market.

In their letter, the senators asked Wheeler to provide his views on these and other issues before Feb. 22.

Wheeler, a longtime Washington insider and former coal lobbyist, took the reins at EPA on an interim basis in July after his predecessor, Scott Pruitt, resigned in a storm of controversy over his high spending on first-class travel, round-the-clock security, and office equipment.

Trump nominated him in January, but a full vote of the Senate is required for his confirmation.