US wholesale inflation came in hot last month. Producer prices rose 6% from a year earlier, most since December 2022, as the 10-week Iran war pushed up energy prices and put pressure on companies to pass along higher costs to consumers.

The Labor Department reported Wednesday that its producer price index — which tracks inflation before it hits consumers — shot up 1.4% in April, biggest monthly gain since March 2022.

Energy prices climbed 7.8% from March to April and 22.7% from a year earlier. Gasoline soared 15.6% from March and diesel, the dominant fuel used in shipping, jumped 12.6%.

Gasoline prices, which have already become painful for many Americans, rose again overnight to a national average of $4.51 per gallon, according to motor club AAA.

Excluding volatile food and energy costs, so-called core producer prices rose 1% from March and 5.2% from April 2025.

All the numbers were much higher than economists had expected and it alters the dynamic at the Federal Reserve and its fight against inflation.

Prices are rising at time when Americans are already frustrated by the high cost of living. Affordability is likely to be a key issue when voters go to the polls Nov. 3 to determine whether President Trump’s Republican Party maintains control of the Senate and House of Representatives.

“This report will set off alarm bells at the Fed and add fuel to the political conversation about affordability,″ Carl Weinberg, chief economist at High Frequency Economics, wrote in a commentary. ”The results are so far above expectations that this update will set off alarm bells in the financial markets, too.″

After the United States and Israel attacked Iran on Feb. 28, Tehran closed off access to the Gulf of Hormuz, through which a fifth of the world’s oil and liquefied natural gas passes. Energy prices raced higher.

Wednesday’s report showed a big uptick in shipping costs. The wholesale cost of truck transportation of freight shot up more than 8% from March and air freight rose 3.6% for the month.

“Diesel fuel is also crucial for food prices, as it powers farm equipment along with commercial shipping and trucking,” wrote Grace Zwemmer, US Economist at Oxford Economics. “Food prices rose by a muted 0.2% in April, much stronger than the 0.6% decline seen in March, and it’s possible they will face upward pressure from higher fuel prices the longer the war persists.”

Wholesale prices can offer an early look at where consumer inflation might be headed. Economists also watch it because some of its components, notably measures of health care and financial services, flow into the Fed’s preferred inflation gauge — the Commerce Department’s personal consumption expenditures, or PCE, price index.

Already this week, the Labor Department said that its closely watched consumer price index jumped 3.8% last month from April 2025 — the biggest year-over-year increase in more than three years — as energy prices continued to climb.

Walmart, a company famous for its intense focus on low prices, already announced rare price hikes last year, and the rising costs may intensify pressure to do so again. It is not alone.

Whirlpool, which makes KitchenAid and Maytag appliances, reported this month that its revenue dropped nearly 10% in its most recent quarter and said that the war has caused a “recession-level industry decline″ that has undermined consumer confidence. It had announced a 10% price hike in April, its largest in a decade, and said that a separate 4% price increase is coming in July.

The cost of credit, which had been in decline, has been frozen in place.

Before the Iran war, the Fed had been expected to cut its benchmark interest rate in 2026. But it has turned cautious as it waits to see how long the conflict lasts and whether higher energy prices spill over into other products and cause a broader inflationary outbreak.

Trump has attacked the Fed and its outgoing chair, Jerome Powell, for refusing to slash rates to boost the economy.

Kevin Warsh, the president’s hand-picked choice to succeed Powell, is expected to be confirmed by the Senate this week; but it’s unclear whether Warsh would pursue lower rates given the uncertainty caused by the war — or whether he could persuade his colleagues on the Fed’s rate-setting committee to go along if he tried.