(Reuters) – U.S. President Donald Trump has agreed to meet with representatives of the oil refining industry and their legislative backers to discuss the nation’s biofuels program, according to two sources briefed on the matter.

The White House meeting could set the stage for negotiations over possible legislation to overhaul the U.S. Renewable Fuel Standard – a 2005 law that requires refiners to blend increasing amounts of biofuels like ethanol into the nation’s gasoline each year, the sources said, asking not to be named.

While the regulation would be a boon to the Midwest corn belt, refining companies oppose it because it cuts into their petroleum-based fuel market share, and because they say the blending requirement costs them hundreds of millions of dollars.

Lawmakers representing both industries have in recent months threatened to block administration nominations over the White House’s handling of the issue, including most recently Texas Senator Ted Cruz – who said he will hold up the nomination of Bill Northey to a federal agriculture post until he gets a meeting with Trump on biofuels.

“The president was briefed, and has agreed on a meeting. Now it is just a matter of finding an hour window,” one of the sources told Reuters. He said he was told by the White House the meeting is likely to be set for the week of Dec. 11.

A White House official declined to comment.

Cruz and eight other senators from states with oil refineries – including Jim Inhofe of Oklahoma, and Pat Toomey of Pennsylvania – had requested the meeting with Trump in a letter in October to discuss the regulation.

In the letter, the senators asked that the meeting include Midwest lawmakers, biofuels representatives and relevant administration officials, so all sides could “discuss a pathway forward toward a mutually agreeable solution.”

It is unlikely Trump would be able to move to reform the biofuels program without buy-in from the corn coalition.

Senator Chuck Grassley of Iowa, a vocal biofuels backer, has said that such a meeting would be a “waste of time.” His office declined to comment on whether Grassley would attend. “No meeting has been scheduled,” his spokesman Michael Zona said.

A spokesman for Senator Cruz did not comment.

The Renewable Fuel Standard was introduced more than a decade ago by then-President George W. Bush as a way to boost U.S. agriculture, slash energy imports and cut emissions.

A number of independent refiners, like Valero Energy Corp, CVR Energy and PBF Energy have vocally opposed the regulation’s requirement that refiners blend the biofuels, or purchase credits from rivals that do – a rule 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 Trump on regulation. During that time he pushed to shift the responsibility for blending away from refiners to supply terminals or distributors.

But Trump’s administration has so far not budged.

The Environmental Protection Agency, which administers the program, slightly increased biofuels volumes targets for 2018 and has rejected proposals to shift the blending burden, or to allow ethanol exports to count towards volumes targets.