U.S. home prices grew more slowly in August amid modest sales, a trend that could help make homes more affordable for buyers in the months ahead.

The Standard & Poor's/Case-Shiller 20-city home price index rose 5.6 percent in August from 12 months earlier. That's down from 6.7 percent in July. Home prices were rising at a double-digit pace as recently as last fall.

The Case-Shiller 20-city index covers roughly half of U.S. homes. The index measures prices compared with those in January 2000 and creates a three-month moving average. The August figures are the latest available.