WASHINGTON (August 15, 2012)—U.S. consumer prices were unchanged in July from June, as a small drop in energy costs offset slightly higher food prices, the U.S. Labor Department said Wednesday.

The consumer price index hasn't changed since March, evidence that the weak economy is keeping inflation in check.

The Labor Department said core consumer prices, which exclude volatile food and energy costs, ticked up 0.1 percent last month.

Higher medical costs, clothing and rents pushed up core prices.

Prices increased 1.4 percent in the 12 months ending in July, down from 1.7 percent in June and the smallest yearly increase in 20 months.

Core prices have increased 2.1 percent in the past year, down from a 2.2 percent pace in June.

Mild inflation gives the Federal Reserve more leeway to take steps to boost growth.