Existing home sales in the U.S. unexpectedly decreased in the month of March, according to a report released Monday by the National Association of Realtors, which attributed the drop in sales to inventory constraints.

NAR said existing home sales fell 0.6 percent to an annual rate of 4.92 million in March after inching up by 0.2 percent to a downwardly revised 4.95 million in February.

The drop surprised economists, who had expected existing home sales to edge up to 5.03 million from the 4.98 million originally reported for the previous month.