WASHINGTON — The nation’s core inflation rate last month grew at the slowest pace in 44 years, offering good news for shoppers at the checkout counter and a bit more breathing room for policy-makers who worry that massive government efforts to spur the economy could trigger higher prices.

But despite these and other short-term benefits, Wednesday’s inflation report raised larger fears that the United States — and the global economy — may be sliding closer to a deflationary spiral that could undermine recovery from the recession.

Deflation is when consumer prices are outright falling. While that might sound like a good thing, it has a powerful tendency to discourage spending, dampen business expansion and forestall new hiring.

And deflationary spirals can be hard to escape from, once they take hold.

“It’s definitely a serious threat,” said Paul Ashworth, senior U.S. economist at Capital Economics in Toronto. “Once falling prices get into the psyche of the people,” he noted, “they tend to delay their spending, and that has knock-on effects on the economy.”

The Bureau of Labor Statistics’ report showed that consumer prices in April declined 0.1 percent from March largely because of a large drop in oil costs.

But the “core” inflation rate, which the federal Reserve and other policy-makers watch more closely because it excludes volatile energy and food prices, was flat in April and up just 0.9 percent from a year ago — the smallest increase since 1966 and the fourth straight month of declining core inflation.

Although consumer spending has picked up in recent months, the latest inflation figures reflected continuing weakness in the housing market and stagnant wages. Both have sapped the buying power of consumers, prompting retailers to slash prices to attract shoppers.

The Fed, in minutes of its most recent meeting that were released Wednesday, also expressed some concern about where inflation was heading.

Even as Fed officials raised their outlook for economic and employment growth, the minutes said they expected inflation to be “somewhat below rates that policy-makers considered to be consistent over the longer run with the Federal Reserve’s dual mandate” of maximizing employment and price stability.

And that meeting came as the Greek debt crisis was just emerging as a threat to the whole European economy and before it began to shake the financial markets in the U.S. — which Fed members said could stall the recovery in the United States.