WASHINGTON — A key U.S. inflation gauge slowed last month as President Donald Trump’s tariffs have yet to noticeably push up prices. Spending by Americans slowed despite rising incomes, potentially an early reaction to higher prices on some imported goods.

Friday’s report from the Commerce Department showed that consumer prices rose 2.1% in April compared with a year earlier, down from 2.3% in March and the lowest since September. Excluding the volatile food and energy categories, core prices rose 2.5% from a year earlier, below the March figure of 2.7% and the lowest in more than four years. Economists track core prices because they typically provide a better read on where inflation is headed.

The figures show inflation still declining from its post-pandemic spike, which reached the highest level in four decades in July 2022. Economists and some business executives have warned that prices will likely head higher as Trump’s widespread tariffs take effect.

On a monthly basis, overall prices and core prices increased 0.1% from March to April. The cost of big-ticket manufactured goods rose 0.5%, although that increase was offset by a 0.1% decline in other goods, such as groceries. The cost of services rose 0.1% from March to April.

The big increase in durable goods prices could reflect the early impact of tariffs.

Overall consumer spending, which includes spending on services, rose 0.2% in April from March, the report said, but that’s down from a 0.7% rise in March.

The slowdown in spending could reflect some early caution on the part of consumers, economists said, in response to higher goods prices. It also suggests that some of the spending jump in March reflected consumers purchasing items like cars to get in front of tariffs.

“The pulling forward of consumer spending ahead of the tariff increases will continue to dampen household spending in the coming months, especially as they face higher prices and a softening labor market,” Kathy Bostjancic, chief economist at Nationwide, said in an email. “We anticipate that the improved inflation trend will reverse in the second half of the year as companies are forced to begin passing along a portion of the increased tariffs in order to protect profit margins.”

Walmart executives said this month that the retail giant would increase prices for many products in May and June to account for the tariffs, while electronics chain Best Buy’s CEO Corie Barry said Thursday that the company is increasing some prices because of the duties, as a “last resort.”

Also Thursday, warehouse retailer Costco said it has already raised prices for some products but has held the line on others. The company largely absorbed the duties on pineapples and bananas “because they are key staple items,” said Gary Millerchip, Costco’s chief financial officer. But the company did increase prices for flowers from Central and South America, for example, “because we felt that was something that the member would be able to absorb.”