Contracts to buy U.S. previously owned homes tumbled unexpectedly in March to snap a three-month rebound, raising a caution flag about what had appeared to be a nascent recovery in a housing market that has been clobbered by rising interest rates.

The National Association of Realtors (NAR) said on Thursday its Pending Home Sales Index, based on signed contracts, fell 5.2% last month to 78.9, the lowest since December. Economists polled by Reuters had forecast pending sales to have increased 0.5% in March, but the reported decline was larger than even the most pessimistic estimate in the survey.

"The lack of housing inventory is a major constraint to rising sales," said NAR Chief Economist Lawrence Yun. "Multiple offers are still occurring on about a third of all listings, and 28% of homes are selling above list price. Limited housing supply is simply not meeting demand nationally."

The housing market has been the sector of the economy most visibly affected by the Federal Reserve's aggressive run of interest rate increases aimed at bringing down inflation, but 2023 had begun with some indications the worst may have passed.

That optimism was dented earlier this month when NAR reported that existing home sales slid 2.4% last month. While some firming has continued in the much-smaller market for new homes, the pending homes data suggests the market's overall recovery is likely to be choppy.

Yun said sales should improve later in the year as he expects continued job growth and mortgage interest rates to fall to about 6% by year end from the current 6.55%.

Contract signings were lower in the Northeast, Midwest and West, while the South saw a fractional gain.