The number of Americans who signed contracts to buy homes fell in September to the lowest level in nine months, reflecting higher mortgage rates and home prices that have made purchases more costly.

The National Association of Realtors said Monday that its seasonally adjusted pending home sales index fell 5.6 percent last month from August to a reading of 101.6. The decline pushed the index below its year-ago level, the first time that’s happened in nearly 2 ½ years.