(Reuters) -U.S. consumers' inflation expectations rose for a second straight month in November despite growing signs that price increases are in fact slowing, according to a survey released Wednesday that may create some worry for Federal Reserve policymakers.

American households see inflation accelerating to 4.5% over the next year, up from 4.2% in October and from 3.2% in September, the University of Michigan's twice-monthly survey of consumer sentiment showed. That is the highest rate since April.

Over a five-year horizon, consumers now see inflation running at 3.2% on average, up from 3.0% in October and 2.8% in September. That is the highest since a matching reading of 3.2% in 2011. Households' long-term inflation outlook has not been higher than that since 2008 when it reached 3.4% as the financial crisis was beginning to unfold.

"These expectations have risen in spite of the fact that consumers have taken note of the continued slowdown in inflation," survey Director Joanne Hsu said in a statement. "Consumers appear worried that the softening of inflation could reverse in the months and years ahead."

U.S. inflation has slowed notably since the summer of 2022 when the annual rate of price increases reached the highest since the early 1980s, prompting the Fed to respond with the most aggressive series of interest rate hikes since that era to try to bring inflation back to its targeted annual rate of 2%.

As measured by the central bank's preferred gauge, price increases of late have been running at 3.4%, down from 7.1% in June 2022. But progress this year has been inconsistent, and Fed officials remain wary of the potential for a reversal.

The Fed's policy rate has remained unchanged at 5.25% to 5.50% since July, and investors are now convinced the tightening cycle is over. Minutes of the Fed's latest meeting earlier this month, released on Tuesday, showed officials agreed they would proceed "carefully" and only raise interest rates further if progress in controlling inflation faltered.

As part of that assessment, Fed officials are keen to see the public's inflation expectations remain well-anchored because accelerating expectations can alter consumer behavior in ways that end up contributing to price increases. In fact a swift run-up in consumer inflation expectations in the spring of 2022 contributed to the Fed's decision to ramp up the pace of rate hikes to three-quarters of a percentage point at four straight policy meetings last year.

"For a data dependent Fed, this is not good news as they do not want to see consumer inflation expectations become unanchored, since historically it becomes increasingly difficult to reset consumer psychology towards a lower inflationary environment," Quincy Krosby, Chief Global Strategist for LPL Financial, said in a note following the latest Michigan survey.

That said, the University of Michigan survey results are at odds with other measures of inflation expectations that have shown they have in fact been moderating. A New York Fed survey of consumers last week, for instance, showed inflation expectations over both one-year and five-year horizons eased in October even as the Michigan survey showed them accelerating.

Market-based measures of inflation expectations are also declining. The so-called breakeven-inflation rates on U.S. Treasury Inflation Protected Securities, also closely followed by Fed officials, are at their lowest in more than month.

(Reporting By Dan Burns; Editing by Chizu Nomiyama)