Sen. Amy Klobuchar (D-Minn.) criticized the latest ethanol proposal from the Trump administration Friday, saying the president hasn't done enough to remedy the past “gut punches” he’s delivered the ethanol industry. 

The 2020 contender stopped by a biodiesel plant while on the campaign trail in Iowa, just hours after the Trump administration proposed changes to the renewable fuel standard designed to boost the use of alternative fuels.

“They've done some really irreversible damage,” Klobuchar said, referring to an August decision to grant 31 waivers to refineries to exempt them from blending in ethanol.

“Any effort is helpful. But this is I fear, too little too late,” she added, saying the proposal still lacked important details.

Those 31 waivers Trump issued in August become a rallying cry for corn farmers because Trump had promised just a few weeks before to reevaluate the exemptions granted to small refineries. 

The waivers also come as Trump’s trade war is closing markets for Iowa corn.

“The one thing they ask the government is do no harm,” Klobuchar said of farmers. “And at least be consistent in your policy so they can make decisions about investment. He's been the opposite. It's been total chaos.”

Though subsidies have been given to many farmers, “that's not a substitute for the business that they want to build,” she said.

Oil companies were also critical of Trump’s ethanol proposal, calling it a political gambit to win votes in a key 2020 state.

“Let’s not sugar coat it, ethanol mandates are being raised because a handful of corn-state senators have extorted it from the president using election year politics,” LeAnn Johnson with the Small Refiners Coalition said in a statement.