Consumer prices jumped 0.7 percent for May, the Labor Department announced on Friday. That is even higher than the 0.6 percent rise predicted by economists and represents the sharpest increase in 20 months.  April's increase was 0.4 percent.

But the so-called core C.P.I., which excludes energy and food, increased a mere 0.1 percent after a 0.2 percent rise in April. The modest rise in core prices, predicted to come in at 0.2 percent, reflects the heavy influence of steep gas prices on the econmy as a whole.

Core C.P.I. is one of the key indicators used to determine the inflation rate, and thus the direction of interest rates. May's modest growth is likely to alleviate investor worries that the Federal Reserve will raise rates anytime soon.