U.S. pending home sales rose slightly in September due to substantial increases in the West and Midwest, the U.S. National Association of Realtors (NAR) said on Thursday.

The Pending Home Sales Index, a forward-looking indicator based on contract signings, increased to 104.6 in September from 104.1 in August. However, contract signings still dropped 1 percent year over year, making this the ninth straight month of annual decreases.

"This shows that buyers are out there on the sidelines, waiting to jump in once more inventory becomes available and the price is right," said Lawrence Yun, NAR's chief economist, adding the unexpected monthly increase is a good, stabilizing trend.

Meanwhile, Yun admitted that the housing market is still restrained by the low inventory of moderately priced homes and affordability.

While pending home sales dropped in the Northeast and South last month, the sales increased in the West and Midwest, according to NAR data.

The Pending Home Sales Index is a leading indicator for the housing sector, based on pending sales of existing homes. A sale is listed as pending when the contract has been signed but the transaction has not closed, though the sale usually is finalized within one or two months of signing.