WASHINGTON (AP) — U.S. wholesale inflation came in hot last month. Producer prices rose 6% from a year earlier, the highest point in more than three years, as the Iran war pushes up energy prices and intensifies pressure on companies to pass along their rising 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, the biggest monthly gain in more than four years.

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 of the numbers released Wednesday caught economists off guard and altered the dynamic at the U.S. Federal Reserve and its fight against inflation.

Prices are rising at a 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 Donald Trump’s Republican Party maintains control of the U.S. Senate and House of Representatives.

“This report will set off alarm bells at the Fed and add fuel to the political conversation about affordability,″ wrote Carl Weinberg, chief economist at High Frequency Economics. “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 Strait of Hormuz, through which a fifth of the world’s oil and liquefied natural gas passes.

The oil shock shows no sign of letting up. The International Energy Agency warned Wednesday that the “mounting supply losses from the Strait of Hormuz are depleting global oil inventories at a record pace.’’ Since February, global oil supplies have been reduced by 12.8 million barrels a day in what the IEA called “an unprecedented supply shock.’’

Wednesday’s report on producer prices 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 prices for consumers may be headed.

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. That has begun to appear in everything from what Americans pay for air travel, both tickets and baggage fees, to soap and toothpaste.

Walmart, a company famous for its intense focus on low prices, already announced rare price hikes last year as Trump’s tariffs were rolled out, 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 another 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, was confirmed by the Senate Wednesday, 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.

Paul Wiseman, The Associated Press