Updated

Fewer Americans signed contracts to buy homes in August, as a shortage of properties for sale is weighing on the market.

The National Association of Realtors says its seasonally adjusted pending home sales index fell 2.4 percent last month to 108.5, its lowest reading since January. The number of signed contracts slumped sharply in the South, the nation's largest housing market. But pending sales improved in the Northeast, Midwest and West.

Pending sales contracts are a barometer of future purchases. A sale is typically completed a month or two after a contract is signed.

Sales have risen much of this year but a slowdown surfaced in August. Completed sales dipped 0.9 percent last month to a seasonally adjusted annual rate of 5.33 million, the Realtors said last week.