Updated

Fewer Americans signed contracts to buy homes in May, with the year-over year pace of pending sales sliding for the first time in nearly two years.

The National Association of Realtors says its seasonally adjusted pending home sales index fell 3.7 percent last month to 110.8, slightly below its May 2015 reading of 111. Overall home sales have steadily improved over the past year. But buyers are facing a shortage of available homes that might have curtailed pending sales last month.

Completed sales of existing homes rose 1.8 percent in May to a seasonally adjusted annual rate of 5.53 million, the highest level since February 2007, the Realtors reported last week. But the number of listings sank 5.7 percent from a year ago, meaning that homebuyers have fewer options.