The number of Americans who signed contracts to buy homes declined in June, following a strong gain in May, a leading U.S. industry group reported Thursday.

The National Association of Realtors (NAR) said its index of pending home sales, which measures the number of contracts to buy previously owned homes that have been signed but not yet closed, slipped 1.4 percent to 99.3 in June, but still posted the 14th consecutive month of year-on-year gains. The reading of May was revised down to 100.7.

NAR chief economist Lawrence Yun said inventory shortages were a factor. "Buyer interest remains strong but fewer home listings mean fewer contract signing opportunities," he noted.

The NAR index is a leading indicator of future existing home sales, since there is usually one or two months' lag between signing a contract and closing a deal.

A reading of 100 indicates an average level of sales activity in 2001, when the index started. The reading was above the 100 threshold from March 2003 to April 2007, and then sank as the country fell into a deep recession caused by the housing debacle.

Yun also saw delays in the contract closing process. "With record low mortgage interest rates, there has been a surge of refinancing on top of a higher level of home purchases, which has been creating delays recently in the closing process," he said.