As U.S. diesel prices climbed to an all-time high this week, President Donald Trump threw his support behind calls from farm-state Republicans for a temporary ban on diesel exports—a move that analysts, industry groups, and even members of his own cabinet warn could backfire on both American consumers and global fuel markets.

"I've said let's not send out the diesel. We make a lot of diesel. I've called for it," Trump said late Tuesday at the U.N. General Assembly in New York.

On its face, the logic seems straightforward: keep more diesel on American soil and prices should fall, sparing farmers, truckers, and all Americans from inflationary pressure. But that is not quite right, according to analysts. Prices might dip for about a month—timed with the midterm elections—before the unintended consequences quickly kick in.

Rather than deliver lasting relief, a ban would unwind much of the U.S. oil and refining industry, drive sky-high gasoline prices further upward, and strip the rest of the world of the U.S. diesel supplies it depends on—a dependence that has only grown since the U.S. initiated the war in Iran and triggered the global energy crisis. Any relief would likely be confined to geographic pockets, such as the U.S. Gulf Coast where most of the fuel is produced, analysts said.

How analysts say it would play out

If the U.S. energy sector were forced to keep its diesel at home, a domestic glut would build quickly and storage would fill to the brim. Refineries would then scale back operations, cutting not only diesel output but also gasoline and jet fuel supplies, because there are no individual switches for each fuel type. Oil producers would in turn limit their activity to prevent a domestic crude glut if refineries stop taking their product.

All of these ripple effects would push oil prices and gasoline and jet fuel costs even higher, while exacerbating diesel costs globally—keeping in mind that fuel prices outside the U.S. are already even higher than at home.

"If diesel exports get banned, [gasoline] prices could rise toward record levels," said Patrick De Haan, head of petroleum analysis at GasBuddy. "The U.S. is not short of diesel. The world is. A potential export ban treats the global price problem as if it was a U.S.-only problem, and the cure would be far worse than the disease."

U.S. Energy Secretary Chris Wright risked bucking Trump on Wednesday, agreeing that a ban would hurt U.S. refining and push up most fuel prices. He offered potential support for voluntary restrictions or some kind of export cap instead. Just a week earlier, at a G20 meeting in Houston, U.S. Interior Secretary Doug Burgum quickly dismissed the idea of a diesel export ban, arguing it would not help lower prices.

Record prices at the pump

The average U.S. diesel price of $6.52 per gallon as of Sept. 23 is an all-time high, still spiking after recently crossing the $6 threshold for the first time. The California average has climbed to $8.43 per gallon, with some stations reportedly maxing out their retail displays at $9.999. For gasoline, the U.S. average of $4.47 per gallon is a post-July record high. The diesel surge also carries weight beyond the pump: the fuel powers trucks, tractors, trains, and ships, so its record price feeds into the cost of food and goods across the economy.

Why fuel costs are so high

So why are fuel costs so elevated while the global oil benchmark remains relatively muted—though still high by historical standards—at just over $100 per barrel? The Iran war is disrupting Middle Eastern refineries from shipping out their products, while Ukrainian drone strikes have knocked out roughly 40% of Russia's refining capacity. Altogether, at least 10% of the world's refining capacity is offline, making the energy crisis more a fuel problem than an oil one—and making the world even more dependent on U.S. fuel supplies than ever.

The bigger global picture must also be considered, De Haan said. "The U.S. spent years becoming the world's backstop for diesel supply. Telling every buyer from South America to Europe that American supply is politically conditional pushes them to diversify away from U.S. refineries and U.S. supplies, softening long-term demand for U.S. product and foregoing political leverage."

Indeed, the U.S. currently supplies about 20% of the world's diesel exports, according to the American Petroleum Institute (API), the lobbying and research group that is sharply against an export ban.

"Restricting U.S. exports would hit an already-tight market with another supply shock," said API CEO Mike Sommers. "The priority should be keeping fuel moving and refineries running, adding new barriers."

Sommers pointed to a further API statement warning that the "consequences would be catastrophic": "Removing that much fuel from the global market would exacerbate the very global refining crisis that is increasing prices here in the U.S. And the impacts could extend far beyond pain at the pump, to dire consequences for international supply chains, agriculture, shipping, manufacturing and the entire global economy."

Trump has been heavily focused on so-called U.S. energy dominance, and an export ban flies in the face of that agenda, said oil forecaster Dan Pickering, founder of the Pickering Energy Partners consulting and research firm.

"Why would you want to undermine that?" Pickering said. "What's bad for the world isn't good for the U.S."

Politics at play

Talk of banning fuel exports has floated in the air for months amid the Iran war, but it never gained momentum until now, despite sharp opposition from the U.S. energy sector. The last time the U.S. briefly banned exports was during the 1970s Arab oil embargo, when the country was far less of an energy exporter.

But now harvest season has picked up in full swing in September, and the agricultural sector is suffering under the weight of record diesel costs—with the midterm elections rapidly approaching.

U.S. Sen. Chuck Grassley, R-Iowa, and other farm-state Republicans are pushing for export bans. "High diesel prices are killing farmers' incomes," Grassley said. Senate Majority Leader John Thune, R-S.D., has also expressed openness to the idea. Oil-state Republicans have pushed back, splitting the party and leaving the matter up to the White House.

"It's maybe another thing that Trump talks about and doesn't do," Pickering said. "It's a growing probability, but still less than 50%."

If a ban did go into effect, Pickering suggested Trump might even consider taking it further and banning gasoline exports as well, causing even more problems globally.

Reserves and the Jones Act alternative

The Strategic Petroleum Reserve—a crude stockpile created after the 1970s Arab oil embargo, the same era that produced the last U.S. export ban—has been depleted throughout the Iran war to 44-year lows, and it is still falling. But the U.S. holds no strategic reserves of gasoline and diesel. In Europe, by contrast, most strategic reserves are kept in refined fuel form—rather than crude oil—although those reserves are not nearly as large. French President Emmanuel Macron is pressing EU nations to coordinate inventory levels and consider the release of more reserves, and Trump's threats to withhold diesel could further pressure them into action.

Another domestic lever would be continuing to extend the Jones Act waiver. The 106-year-old Jones Act, formally the Merchant Marine Act of 1920, requires cargo ships moving between U.S. ports to be U.S.-built, -flagged, and -manned, which reduces the number of vessels available to move crude oil and refined products between domestic ports. Waiving the Jones Act during the Iran war has allowed more ships, for instance, to move fuel from the U.S. Gulf Coast through the Panama Canal and up to California—which has dealt with newly shuttered refineries in recent months—to help alleviate shortfalls.

De Haan encouraged the White House to instead simply extend the Jones Act waiver beyond its Nov. 15 expiration. "The Jones Act waiver is already doing a lot of work here, moving the surplus to where it's needed," he said, adding that an export ban creates far too many problems.

"Export bans are usually quick to go into place and slow to unwind, bringing lasting damage," De Haan added.

The calendar offers the nearest markers: the Jones Act waiver expires Nov. 15 and the midterm elections are weeks away, keeping fuel policy at the center of the White House's agenda through the fall.

This story was originally featured on Fortune.com.