President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE has stopped an expected deal to change how the federal government enforces the federal ethanol mandate.

Iowa GOP Sens. Chuck Grassley Charles (Chuck) Ernest GrassleyThe Hill's 12:30 Report: Ginsburg lies in repose Top GOP senators say Hunter Biden's work 'cast a shadow' over Obama Ukraine policy Read: Senate GOP's controversial Biden report MORE and Joni Ernst Joni Kay ErnstThe Hill's Campaign Report: GOP set to ask SCOTUS to limit mail-in voting Liberal super PAC launches ads targeting vulnerable GOP senators over SCOTUS fight Romney backs pre-election Supreme Court vote, paving way for McConnell, Trump MORE both tweeted the news late Tuesday, and a source familiar with the matter confirmed it.

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The White House was expected this week to unveil a deal that would have, among other measures, counted exported ethanol toward the annual volume mandates under the Renewable Fuel Standard, effectively decreasing the amount of ethanol that must be blended into the nation’s gasoline.

Trump “helped farmers by rejecting bad ethanol deal. I appreciate. GREAT NEWS,” Grassley tweeted.

@realDonaldTrump Pres Trump helped farmers by rejecting bad ethanol deal. I appreciate. GREAT NEWS — ChuckGrassley (@ChuckGrassley) June 5, 2018

Ernst tweeted that Trump “just assured me he 'won’t sign a deal that’s bad for farmers!' Thank you, Mr. President!”

. @realDonaldTrump has said he “looovves the farmers!” #Iowa is feeling that love today, as the President just assured me he “won’t sign a deal that’s bad for farmers!” Thank you, Mr. President! — Joni Ernst (@SenJoniErnst) June 5, 2018

Iowa dominates the country's corn production, the feedstock that produces most of the country’s ethanol.

The Trump administration deal would have also removed restrictions on selling gasoline with high ethanol concentrations in the summer, a move supported by ethanol backers.

Grassley and Ernst had spent Tuesday chastising Environmental Protection Agency Administrator Scott Pruitt Edward (Scott) Scott PruittJuan Williams: Swamp creature at the White House Science protections must be enforceable Conspicuous by their absence from the Republican Convention MORE — whose agency is responsible for the ethanol mandate — over the expected agreement.

Ernst said at an event that Pruitt “is about as swampy as you get here in Washington, D.C. … and if the president wants to drain the swamp, he needs to take a look at his own Cabinet.”

She was referring specifically to Pruitt's spending and ethics scandals, but her main anger at Pruitt was over ethanol.

“This is a case where the president is being ill-served by political appointees that aren't carrying out his agenda,” said Grassley.