Diesel averaged $6.51 per gallon across the U.S. on Thursday, up $2.82 from a year earlier — and the country's largest business groups are now warning President Donald Trump that an export ban would push that number higher, not lower.

The U.S. Chamber of Commerce, Business Roundtable, National Association of Manufacturers, American Petroleum Institute and dozens of allied organizations delivered a joint letter to Trump on Wednesday. They argued that a ban would "lead to less fuel production, tighter supplies and rising costs for American families, farmers and truckers," according to CNBC.

"You have been asked by some to ban or limit the export of diesel to help lower prices, when in fact the opposite would occur," the groups wrote.

What does the ban proposal actually involve?

Trump said Tuesday, on the sidelines of the U.N. General Assembly, that he has pushed the idea inside his own administration. "I've said let's not send out the diesel. We make a lot of diesel," he told reporters.

Treasury Secretary Scott Bessent said the White House is testing whether a full or partial ban is "feasible in terms of the overall refining capacity." No decision has been announced, and no timeline has been set.

For refiners and fuel buyers, the mechanics matter more than the rhetoric. Energy experts cited by CNBC expect a ban to send diesel prices sharply downward in some U.S. regions at first, then rebound even higher once refiners cut output to offset lost export markets.

Why the pushback cuts across Trump's own Cabinet

The opposition is not coming only from trade associations. Neil Bradley, chief policy officer at the U.S. Chamber of Commerce, said the U.S. — the world's largest diesel exporter — risks triggering "a cascading effect across energy markets, driving up costs for consumers, squeezing U.S. refiners, and jeopardizing supplies of gasoline and jet fuel that Americans depend on every day."

Former Energy Secretary Dan Brouillette, who served in Trump's Cabinet from 2019 to 2021, told CNN the proposal makes "very little economic sense." His reasoning is structural: diesel and gasoline come from the same crude barrel, so any pullback in diesel refining squeezes gasoline production and tightens total fuel supply.

Current Energy Secretary Chris Wright has also distanced himself from the idea. "The blunt tool of banning diesel exports definitely doesn't work," Wright told CNN at a New York event on Wednesday. He told the New York Times that "nobody wants a full blanket ban or zero exports of diesel" and that the real discussion centers on moving more diesel into the U.S. while keeping gasoline and jet fuel flowing.

What is driving the price spike?

Ukrainian strikes on Russian refineries and the U.S.-Iran conflict have disrupted global refining capacity and shipping lanes. Before Moscow imposed its own export ban, Russia ranked as the world's second-biggest diesel supplier — a reminder that export restrictions have already reshaped this market once.

The price chart explains the political urgency. AAA data cited by CNBC puts the national diesel average at $6.51 per gallon, a jump of $2.82 year over year.

Trump also faces pressure from his own party. Republican lawmakers in farm states, watching November's midterm elections, want action on fuel costs. Iowa Sen. Chuck Grassley called over the weekend for a diesel export embargo, arguing that record prices are devastating American farmers and truckers.

What should practitioners watch next?

Three factors will decide whether this becomes policy or positioning:

• Whether Bessent's feasibility review concludes that U.S. refining capacity can absorb a partial restriction without cutting gasoline and jet fuel output.
• Whether Trump overrides the unified objection of the Chamber, API, manufacturers and his own Energy Secretary.
• Whether diesel prices keep climbing toward the midterms, hardening the farm-state demand for an embargo.

The clearest signal so far: every institution with direct knowledge of refining economics — including the two men who have run the Energy Department under Trump — has rejected the ban's central premise.