U.S. Consumer Price Index (CPI) rose moderately in June, led by strong increase of gasoline prices.

As a main gauge of inflation, the CPI increased 0.3 percent on a seasonally adjusted basis last month, after an increase of 0.4 percent in May. Over the last 12 months, the index increased 2.1 percent before seasonal adjustment.

In contrast to the broad-based increase last month, consumer prices in June were primarily driven by the gasoline prices which rose 3.3 percent and accounted for two-thirds of the all items increase.

Energy prices increased 1.6 percent in June from a month earlier, while food costs gained 0.1 percent, the Labor Department said.

Excluding the volatile food and energy categories, the so-called core CPI rose 0.1 percent in June after a 0.3 percent increase in May. The core CPI was up 1.9 percent in the past 12 months, which was in line with the Federal Reserve's inflation target of 2 percent.

Economists monitor core prices to get a sense of broader inflation trend, a key barometer for monetary policy decision of the central bank. The rising core prices indicate that U.S. inflation has bottomed out and is heading back toward the Fed's target. That should comfort some Fed officials who had worried inflation was running too low.

The central bank started a two-day monetary policy meeting Tuesday. Economists expect the Fed to continue trimming its monthly bond purchase program, and wait until 2015 to begin raising its benchmark interest rates.