Sales of new U.S. single-family homes unexpectedly increased in April as builders lowered prices to lure buyers, but rising mortgage rates and an uncertain economic outlook remain constraints for the housing market.

Previously owned homes were sold in April at a seasonally adjusted annual rate of 4 million, below consensus estimates that called for a rise to 4.1 million.

Sales of previously owned homes in April declined 0.5% from March to a seasonally adjusted, annualized rate of 4 million units, according to the National Association of Realtors. That is the slowest April pace since 2009.