U.S. single-family home prices accelerated at a slower pace than expected in April, a survey showed on Tuesday.

The S&P CoreLogic Case-Shiller composite index of 20 metropolitan areas rose 5.7 percent in April on a year-over-year basis, after an unrevised 5.9 percent increase inMarch. April's result fell short of the 5.9 percent increase forecast in a Reuters poll of economists.

Despite coming in below expectations, David M. Blitzer, managing director and chairman of the index committee at S&P Dow Jones Indices, said the supply of homes has barely kept up with demand and inventory of new or existing homes for sale had diminished to a 4-month supply. That is likely to keep home prices on the rise.

"Since demand is exceeding supply and financing is available, there is nothing right now to keep prices from going up," Blitzer said.

On a monthly basis, prices in the 20 cities rose 0.3 percent in April on a seasonally adjusted basis, the survey showed, short of expectations calling for a 0.4 percent increase.

On a non-seasonally adjusted basis, prices increased 0.9percent from March.

Reuters (Reporting by Chuck Mikolajczak; Editing by Chizu Nomiyama)