President Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE gave rallygoers in Iowa on Tuesday a sign of what might come in 2020, speaking to them about ethanol while taking hard jabs at Democratic presidential candidate Joe Biden Joe BidenPelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Hillicon Valley: Subpoenas for Facebook, Google and Twitter on the cards | Wray rebuffs mail-in voting conspiracies | Reps. raise mass surveillance concerns Fox News poll: Biden ahead of Trump in Nevada, Pennsylvania and Ohio MORE.

Speaking in Council Bluffs, Iowa, to celebrate his administration’s decision to allow 15 percent of ethanol to be mixed into gasoline in the hot summer months, Trump in one breath called the move an American success story while also blasting Biden for failing to embrace the fuel under former President Obama.

"America must never be held hostage to foreign suppliers of energy as we have under Sleepy Joe," Trump told the crowd gathered at Southwest Iowa Renewable Energy, using his preferred nickname for the former vice president.

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"Under the previous administration, our leaders rejected American energy and they rejected ethanol. They imposed radical restrictions on our farmers, refused to allow talk of E-15 during the busiest driving time of the year," Trump said, nodding to both Biden and Obama. "How ridiculous was that?"

Biden is leading the polls as the top Democratic contender. He was visiting Iowa the same day as Trump to hold his own rally.

Trump was visiting the largest state producer of corn to promote his late-May decision to expand requirements to blend gasoline with 15 percent ethanol year-round, a move that generated cheers from the farming industry but was met with frustration by the oil and gas sector.

The Obama administration had previously ruled to limit the sale of the higher blend of ethanol during the summer months because of scientific studies that showed burning ethanol in warmer temperature leads to heightened ground-level ozone pollution and smog. Instead, the administration allowed sales of E-10 between June 1 and Sept. 15.

Trump ducked the science behind the administration's decision, telling the crowd Tuesday he was never told why the sales were not allowed year-round.

"No one could explain to me why," he said. "But we ended it."

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Instead, he told the crowd that Obama and Biden’s decision was a detriment to the economy.

“You were taken advantage of by stupidity, by incompetence, by people who don’t care. You were treated very badly, but you aren’t being treated badly anymore.” he said.

The president called his divisive decision a win for American energy.

“More American ethanol production means less dependence on foreign supplies,” Trump told the crowd. “Quite simply, it means more energy. And what can be wrong with that? And it’s very good energy.”

Trump also took a page out of his 2015 primary debate playbook, reminiscing about his time spent trying to win over votes in the state. He noted that he felt he had come a long way.

“We came here, and we talked about ethanol, and people didn’t believe it, and now it’s a big beauty,” he said.

“It’s come a long way from our first conversation, hasn’t it? You’ve come a long way. So have I. I’ve become president,” he added.