WASHINGTON — More U.S. small-business owners raised prices in April than at any time in the past seven months even as optimism about the economy dimmed and sales prospects stalled, a private survey found.

The National Federation of Independent Business' index of business optimism fell 0.5 percentage point during the month to 96.8, the lowest since December, the Washington-based advocacy group said. A net 18 percent of owners said they raised prices last month, the most since September.

The report may be unwelcome news for Federal Reserve policymakers who meet tomorrow to decide the course of interest rates. Central bankers have predicted that inflation will slow along with the economy.

"Price pressures are heading up, not down," William Dunkelberg, chief economist at the Philadelphia-based NFIB said in a statement. This year "is not unfolding in the Fed's favor. Growth is slower, but inflation pressures are increasing."

Federal Reserve policymakers will keep the target for the benchmark overnight lending rate unchanged at 5.25 percent for a seventh consecutive policy meeting tomorrow, according to the unanimous forecast of economists surveyed by Bloomberg News.

In their policy statement on March 21, officials said inflation remained their "predominant" concern.

Minutes of the Fed's March policy meeting, released April 11, showed that most participants at the meeting acknowledged recent inflation and productivity data "increased the odds that inflation would fail to moderate as expected."

The NFIB's price measure, which rose 3 percentage points from 15 in March, needs to fall to around 5 percent to signal the Fed's preferred inflation gauge will drop within most central bankers' comfort zone of 1 percent to 2 percent, Dunkelberg said.

The report also showed fewer small-company owners than at any time since August projected the economy would improve over the next six months. The index of those planning to expand their businesses was unchanged at an almost four-year low and the net proportion expecting better sales was unchanged at 14 percent, the fewest since August.

The lack of optimism is also reflected in reduced plans to invest in new factories and equipment.

A net 29 percent of business owners said they expect to boost capital spending, down 4 percentage points from the prior month and the lowest this year.