Prices of U.S. single-family homes in March fell 18.7 percent from a year earlier, while prices in the first quarter dropped at a record pace, according to the Standard & Poor's/Case-Shiller Home Price Indices released on Tuesday.

On a month-over-month basis, the index of 20 metropolitan areas fell 2.2 percent in March from February, S&P said in a statement.

Price drops on both a month-over-month and year-over-year basis were worse than expectations based on a Reuters survey of economists.

The composite index of 10 metropolitan areas declined 2.1 percent in March from February for a 18.6 percent year-over-year drop.

Declines in residential real estate continued at a steady pace into March, David M. Blitzer, Chairman of the Index Committee at Standard & Poor's, said in a statement.

However, he noted it was the second month since October 2007 in which the 10- and 20-City Composites did not drop at a record annual pace.

(Reporting by Julie Haviv, Editing by Chizu Nomiyama)