U.S. consumer prices rose less than expected in September, held back by a slower increase in the cost of rent and falling energy prices, as underlying inflation pressures appeared to cool slightly.

The Consumer Price Index increased 0.1 percent last month after rising 0.2 percent in August. In the 12 months through September, the CPI increased 2.3 percent, slowing from August's 2.7 percent advance.

Excluding the volatile food and energy components, the CPI edged up 0.1 percent for the second straight month. The so-called core index had increased 0.2 percent in May, June and July.

In the 12 months through September, the core CPI increased 2.2 percent. Economists polled by Reuters had forecast both overall and core CPI climbing 0.2 percent in September.

With the readings only slightly below what analysts expected, the inflation report will probably do little to change expectations that the Federal Reserve will raise interest rates at its December policy meeting. The U.S. central bank has raised rates three times this year.