WASHINGTON—Contracts to buy U.S. previously owned homes unexpectedly fell in September likely as some potential buyers delayed purchases amid higher prices. The National Association of Realtors (NAR) said on Thursday its Pending Home Sales Index, based on signed contracts, decreased 2.3 percent last month to 116.7. Pending home sales fell in all four regions. Economists polled by Reuters had forecast contracts, which become sales after a month or two, would be unchanged. Pending home sales dropped 8.0 percent in September on a year-on-year basis. Scarce inventory has led to double-digit growth in home prices. “Some potential buyers have momentarily paused their home search with intentions to resume in 2022,” said Lawrence Yun, NAR’s chief economist. Demand for housing surged early in the coronavirus pandemic amid an exodus from cities to suburbs and other lower-density locations as Americans sought more spacious accommodations for home offices and online schooling. The buying frenzy …