DES MOINES, Iowa (AP) — Iowa ethanol and biodiesel producers are warning President Donald Trump that imposing restrictions on biofuels production “would be viewed as a declaration of war on rural America.”

The Iowa Renewable Fuels Association, representing refineries in the nation’s largest biofuels producing state, called on Sens. Charles Grassley and Joni Ernst on Friday to reach out to Trump. The refiners use corn, soybeans and animal fat to make biofuels and want the senators to tell Trump limiting biofuel production is a “complete abdication of his repeated promises” to protect biofuels.

The group says it’s heard that EPA Administrator Scott Pruitt plans to push Trump on Monday for a proposal that would cut biofuel demand. Farm states, already stinging from Trump’s tariff fight with China, are alarmed he could further hurt ag markets.