Limited supplies of housing inventory restrained existing-home sales to an annual rate of 4.55 million units last month, while home prices continued on a general uptrend in all regions, according to the National Association of Realtors.

Sales of existing homes – completed transactions of single-family homes, townhouse and condos – declined 1.5 percent in May, but are 9.6 percent above the 4.15 million-unit pace of a year ago.

Inventory shortages in certain areas have been developing since the beginning of the year, said Lawrence Yun, NAR chief economist,

“The slight pullback in monthly home sales is more likely due to supply constraints rather than softening demand,” Yun said. “The normal seasonal upturn in inventory did not occur this spring,”

Even with May’s decline, existing home sales have recorded 11 consecutive months of gains over the same month a year earlier.

There are broad-based shortages of inventory in the lower price ranges in much of the country, except the Northeast. In the West, supply is extremely tight in all price ranges, except for the upper end.

Realtors in Western states have been urging lenders to expedite the process of getting additional foreclosed properties onto the market because they have more buyers than available property, Yun said.

Widespread inventory shortages also are found in much of Florida.

Total housing inventory at the end of May slipped 0.4 percent to 2.49 million existing homes available for sale, which represents a 6.6-month supply at the current sales pace. There was a 6.5-month supply in April.

Listed inventory is 20.4 percent below a year ago when there was a 9.1-month supply.

Unsold inventory has trended down from a record 4.04 million in July 2007; supplies reached a cyclical peak of 12.1 months in July 2010.

“The recovery is occurring despite excessively tight credit conditions and higher down-payment requirements, which are negating the impact of record high affordability conditions,” Yun said.