(Reuters) - Nine U.S. senators from states that have oil refineries sent a letter to President Donald Trump on Thursday urging changes to the country’s biofuels policy and asking for a meeting to discuss the issue.

File photo: A fuel nozzle from a bio diesel fuel pump is seen in this photo illustration taken at a filling station in San Diego, California January 8, 2015. REUTERS/Mike Blake

The letter reflects growing tensions between refiners that oppose the U.S. Renewable Fuel Standard - a law requiring them to blend increasing amounts of ethanol into the nation’s fuel each year - and the Midwest corn lobby that supports it.

The Trump administration bowed to rising pressure from Midwest lawmakers last week, assuring them in letters and phone calls that it would ditch proposals, supported by the refining industry, to overhaul the biofuels policy.

The senators said that decision could cost jobs.

“If your administration does not make adjustments or reforms on matters related to the Renewable Fuel Standard, it will result in a loss of jobs around the country, particularly in our states,” according to the letter, which was signed by Texas Senator Ted Cruz, Oklahoma Senator Jim Inhofe, Pennsylvania Senator Pat Toomey and six others.

In the letter, the senators asked Trump for a meeting within the next three weeks that would include them, a number of Midwest lawmakers and relevant administration officials “to discuss a pathway forward toward a mutually agreeable solution.”

A White House official did not immediately respond to a request for comment on the meeting request.

The Renewable Fuel Standard was implemented by former President George W. Bush in 2005 as a way to support farmers, reduce imports and combat climate change.

The oil industry has opposed the regulation, mainly because the increasing biofuels volume mandates cut into their petroleum-based fuel market share.

A number of independent refiners, like Valero Energy Corp, CVR Energy and PBF Energy are also vocally opposed to the regulation’s requirement that refiners blend the biofuels or purchase credits from rivals that do - which they say costs them hundreds of millions of dollars each year.

CVR’s majority owner, billionaire Carl Icahn, served for months as a top adviser to Donald Trump on regulation and during that time pushed to shift the responsibility for blending away from refiners to supply terminals or distributors. He resigned from his post this summer over concerns about his dual role as an investor and adviser.

The Environmental Protection Agency said last week that it did not believe shifting the blending requirement off refiners was appropriate. The EPA also jettisoned a proposal to cut biofuels volumes mandates, and another to count ethanol exports against those mandates.