(Bloomberg) -- President Donald Trump met Wednesday with the heads of two of the nation’s largest refiners as he seeks a deal that would boost corn-based ethanol and soy-based biodiesel without alienating oil companies required to use the products.

Trump met with Marathon Petroleum Corp. chief executive Gary Heminger; Valero Energy Corp. chief executive Joe Gorder; and Harold Hamm, the founder of Continental Resources Inc., according to people familiar with the matter who asked not to be named describing private discussions. Although Hamm’s Continental is an oil producer without direct involvement in U.S. biofuel mandates, the president has long tapped the billionaire oilman’s energy expertise.

White House officials are set to meet Thursday with senators from corn- and ethanol-producing states, amid deep anger in the Midwest U.S. over the Environmental Protection Agency’s decision waive some oil refineries from annual blending quotas.

Administration officials have spent weeks trying to develop a suite of pro-ethanol and pro-biodiesel policy changes that would temper the angst in Iowa and other politically important Midwest U.S. states. But they’re trying to do it without prompting a backlash in the Rust Belt, even as oil industry workers and labor unions demonstrated their opposition with a rally in Toledo, Ohio, on Thursday.

Ethanol manufacturers and Iowa politicians have been cool to a drafted White House plan that would give a 5% boost to biofuel-blending requirements in 2020 and are asking the administration to do more to formally account for refinery exemptions as part of the quotas. In a separate meeting Wednesday, White House officials told biofuel producers to swiftly offer alternatives to that plan, warning that they are running out of time to make changes to proposed 2020 quotas.

Refining representatives, who also met with National Economic Council staff on Wednesday, are pressing the administration to find ways to constrain the cost of tradable credits known renewable identification numbers, which are used to prove they have fulfilled biofuel-blending requirements. Although refinery exemptions have driven down the cost of those compliance credits, any move to boost future quotas threatens to propel their prices again.

Some refiners are advancing a plan that would allow the EPA to sell its own compliance credits whenever those RINs prices get too high. The EPA-generated credits would not be tied to actual biofuel production or blending but revenue from their sale could be steered to building out fueling infrastructure to get more ethanol to consumers.

Marathon Petroleum spokesman Jamal T. Kheiry confirmed Wednesday’s meeting, saying the company “always appreciates the opportunity to share our thoughts with elected officials on policies that can impact our business and consumers who rely on our products.”

Asked about Hamm’s involvement, Kristin Thomas, a senior vice president with Continental Resources, said: “Mr. Hamm is supportive of the president and his positive impact on American energy.”

Representatives for Valero did not immediately respond to requests for comment.

(Updates with more details on White House meetings from third paragraph.)

--With assistance from Josh Wingrove.

To contact the reporters on this story: Jennifer A. Dlouhy in Washington at jdlouhy1@bloomberg.net;Mario Parker in Chicago at mparker22@bloomberg.net;Jennifer Jacobs in Washington at jjacobs68@bloomberg.net

To contact the editors responsible for this story: Jon Morgan at jmorgan97@bloomberg.net, Elizabeth Wasserman

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