Higher costs and tight market conditions have taken a toll on buyer enthusiasm, the National Association of Realtors said.
The NAR Pending Home Sales Index slid 1.6 percent in August to 107.7, after dropping in June and July.
The index hit a six-year high in May. But rising interest rates and home prices, tight inventory and restrictive credit conditions have mounted up, NAR said.
In addition, summer produces a seasonal surge in home sale closings, which disrupted the market's momentum.
The index remains 5.8 percent higher than August 2012, when it stood at 101.8.
Pending home sales, which reflect sales activities one and two months down the road, is a comparison to the monthly average for 2001, its first year, which was assigned a value of 100.
The NAR said the Pending Home Sales Index for the Northeast rose 4 percent to 84.8, although it came in 5.1 percent higher than August 2012.
In the Midwest, the index, dropped 1.4 percent to 111.6, reaching a level 13.8 percent higher than August 2012.
The index fell 3.5 percent in the South to 116.9, which is 3.7 percent higher than 12 months prior. In the West, the index came to 106.9, down 1.6 percent from July, but up 1.7 percent from August 2012.
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