At a Thursday-night rally in Iowa, President Donald Trump railed against the Green New Deal championed by progressive Democrats like Rep. Alexandria Ocasio-Cortez and Sen. Bernie Sanders.

"Don't say it. They want to kill our cows. That means you're next," the president told supporters in Des Moines.

The Green New Deal proposes working with farmers to help tackle greenhouse-gas emissions from agriculture, but it does not mention confiscating livestock or murdering humans.

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President Donald Trump has launched a bizarre attack on the Green New Deal championed by progressive Democrats like Rep. Alexandria Ocasio-Cortez and Sen. Bernie Sanders, telling a rally in Iowa on Thursday night that "they want to kill our cows" and, eventually, American farmers.

"During this campaign season, the good people of Iowa have had a front-row seat to the lunacy and the madness of the totally sick left," Trump told the crowd in Des Moines.

"The Green New Deal, which would crush our farms, destroy our wonderful cows. They want to kill our cows. You know why, right? You know why?"

"Don't say it. They want to kill our cows. That means you're next," he said, as the crowd laughed.

The Green New Deal has become a favored punching bag for Trump on the campaign trail, as he seeks to whip up hostility to proposals meant to curb fossil-fuel emissions.

Studies by the US Environmental Protection Agency have linked about 9% of US greenhouse emissions to agriculture, including methane from cows belching.

The deal mentions working collaboratively with farmers and livestock owners to reduce greenhouse emissions but does not mention cows — let alone murdering humans.

Rep. Alexandria Ocasio-Cortez at a House Financial Services Committee hearing in October. MANDEL NGAN/AFP via Getty Images

Iowa is one of the key battleground states of the 2020 campaign, and Trump is fighting to retain the support of farmers who have been hit hard by his yearlong trade war with China.

In his speech, Trump went on to boast of his own policies and railed against the impeachment trial being conducted in Washington as he spoke.

"We're having probably the best years that we've ever had in our country, and I just got impeached!" he said.

"Can you believe these people? I got impeached. They impeached Trump."

Referring to House Democrats, he added: "They want to nullify your ballots, poison our democracy, and overthrow the entire system of government. That's not happening — I can tell you that."

Trump and other Republicans have repeatedly accused Democrats of concocting what they say are bogus impeachment allegations as part of a plot to end Trump's presidency before the November elections.