Washington ? Rising prices for gasoline, air travel and clothing propelled consumer costs 0.5 percent higher in March, raising the possibility that the Federal Reserve may increase interest rates this summer.

Wednesday’s reading on the Consumer Price Index, the government’s most closely watched inflation measure, resurrected concerns about the prospects of an inflation flare-up now that the economy is rebounding, economists said.

The report by the Labor Department “confirms my worst fear: Inflation is rising,” said Stephen Cecchetti, economics professor at Brandeis University. “Details confirm that the inflation increase isn’t in some isolated place, or the consequence of some special factor.”

The 0.5 percent increase was up from February’s 0.3 percent advance and matched January’s figure.

Especially jolting was the 0.4 percent increase in “core” consumer prices, excluding energy and food costs. That was double the 0.2 percent in both January and February.

The latest snapshot of the inflation climate showed consumer prices moving up more quickly than expected. And it “solidifies the path toward a Fed tightening move this summer,” said Mark Zandi, chief economist at Economy.com.

With the economy rebounding, some companies are beginning to have a greater ability to raise product prices, economists said. Rising energy costs in some cases are being passed along to consumers in the form of higher prices, analysts added.

“It’s been a long time coming, but it appears that pricing power has begun to return,” said Joel Naroff, president of Naroff Economic Advisors. “The day the Fed raises rates is coming sooner than many thought.”

Zandi and other economists believe a rate increase of one-quarter percentage point could come in August — before the presidential election in November. That might upset voters and could irk President Bush, economists said. Others, however, don’t foresee the Fed raising rates until 2005. Most analysts agree that the Fed probably will keep rates steady at its next meeting in May.