The nationwide average price of diesel reached $6 per gallon Friday for the first time, setting a troubling record for a fuel that is essential to large portions of the U.S. economy.

AAA reported that diesel stood at $6.05 per gallon Friday morning. Meanwhile, the national average for regular gasoline was $4.29 per gallon, an increase of 15 cents from the previous week.

Since the war with Iran began in late February, the national average price of diesel has surged 60%.

“The cost of diesel gets into just about everything,” KPMG chief economist Diane Swonk said in a recent interview.

“From running a farm … [to the] cost of food, but also everything across the economy that’s shipped,” she said. When diesel prices rise, everything “gets that extra fee tacked onto it.”

Swonk said the elevated price of diesel could become an “inflationary problem” that persists for months.

Since late July, diesel prices have increased more rapidly and by a greater amount than regular gasoline prices.

One reason is that important refineries responsible for producing diesel have been taken offline or destroyed in both Eastern Europe, amid the ongoing Russia-Ukraine war, and the Middle East.

Although fossil-fuel markets have been affected this year by the blockade of the Strait of Hormuz, diesel has its own supply pressures. Unlike crude oil and regular gasoline, the diesel market is particularly affected by the major role Russian refineries play in worldwide supplies.

Russia generally exports more diesel than any other country except the United States. However, damage to Russian refineries caused by Ukrainian drone attacks led the Kremlin to impose a broad diesel export ban in July. The restrictions are expected to remain in place at least through the end of September.

“Consumers should be prepared to pay higher inflation for anything that requires being shipped,” Joseph Brusuelas, chief economist at the RSM management consulting firm, told NBC News.

‘Economic carnage’

Higher diesel costs are expected to put particular pressure on grocery prices, Brusuelas said. Supermarkets are already dealing with extremely narrow profit margins, partly because beef prices have risen sharply.

But the effect on food prices extends well beyond supermarkets. Higher diesel costs can increase expenses throughout the entire food-supply chain, beginning with farmers and continuing through transportation and distribution.

For some U.S. farmers, the $6-per-gallon diesel price could make an already difficult financial situation even worse. Many are also dealing with pressure from a fertilizer shortage this year.

“It’ll push me right to the edge,” said Mark Mueller, a fourth-generation Iowa farmer. “If I don’t get pushed over the edge by diesel fuel prices, higher fertilizer prices will push me over the edge because a lot of petroleum goes into fertilizer prices, as well.”

Mueller said the combination of higher diesel and fertilizer expenses could significantly reduce or eliminate farmers’ profits.

As long as the war in Iran keeps sending prices higher for necessities like diesel and fertilizer, he said, “we are endangering one of the strongest economic pillars that we have in this country through economic uncertainty, higher prices.”

“We’re shooting ourselves in the foot, and we don’t have to,” said Mueller, who chairs the Iowa Corn Growers Association.

No relief in sight

Mueller is not the only person expressing concern about the domestic economic consequences of the war in Iran and its effect on prices.

As Republicans met in Dallas this week for what President Donald Trump called a midterm election convention, a new NBC News poll found that roughly 70% of voters disapproved of his handling of the Iran war.

“I just see economic carnage the longer this war goes on,” Mueller said.

For more than six months, Trump has maintained that the war with Iran would be brief. This week, however, he acknowledged that gasoline prices may remain elevated for some time.

“I think it’s going to take a little bit longer than the midterms” for the cost of gas to fall again, he told reporters en route to Dallas. “Right after the election, oil prices are going to be tumbling downward.”

U.S. crude oil prices have increased by more than 25% over the past month.

Diesel, meanwhile, has been following a longer-term upward trend dating back to 2022, when Russia invaded Ukraine. In June of that year, the U.S. average diesel price reached a then-record $5.82 per gallon.

Although diesel prices subsequently declined, they have not returned to their pre-2022 levels.

Diesel prices surged again this spring after the U.S. and Israel’s war with Iran led to the closure of the Strait of Hormuz and disrupted energy supplies worldwide.

The latest increase in diesel prices is again being linked to the Russia-Ukraine war, more than four years after the conflict first helped set diesel prices on a higher trajectory.