President Donald Trump has cited his move to allow year-round sales of high-ethanol gasoline as farmers pressure him to dial back decisions to exempt oil refineries from biofuel-blending mandates, signaling the president sees the two issues as related.

The Trump administration on March 12 advanced a plan meant to expand the U.S. market for corn-based ethanol and place trading restrictions on credits that refiners use to prove they are using biofuel.

President Donald Trump’s pledge to his rural agricultural base to allow year-round sales of higher blends of ethanol spurred differing opinions between key federal agencies Feb. 27.

Marathon Petroleum Corp., the largest U.S. oil refiner after its $23.3 billion acquisition of rival Andeavor this month, is weighing a plan to start sales of high-ethanol gasoline at its stations in Minnesota, according to people familiar with the matter.