Single-family home prices unexpectedly climbed in April from March, driven by a final sales push before tax credits expired, but signs of a sustained recovery have yet to emerge, Standard & Poor's/Case Shiller home price indexes showed on Tuesday.

Inventory data and foreclosure activity have not shown any signs of improvement, David Blitzer, chairman of S&P's index committee, said in a statement. Consistent and sustained boosts to economic growth from housing may have to wait to next year.

The S&P composite index of home prices in 20 metropolitan areas for April rose 0.4 percent on a seasonally adjusted basis after a downwardly revised 0.2 percent drop in March, compared with a 0.1 percent decline forecast in a Reuters survey. March prices were previously reported as unchanged.

On an unadjusted basis, prices gained 0.8 percent in April following March's 0.5 percent drop. A 0.2 percent rise was forecast in a Reuters poll.

The 20-city index rose 3.8 percent in April from a year earlier, topping the expected 3.4 percent increase.

Home sales have fallen precipitously in the weeks since the April 30 end of tax credits of up to $8,000, which pushed sales forward as buyers raced to lock in the incentive.

Other reports have shown sales of new homes sank by a record 32.7 percent in May to the lowest level since record keeping began in the early 1960s, and existing home sales unexpectedly fell 2.2 percent in May.

Applications to buy homes hover at 13-year lows.

Still, affordability is high, with prices down around 30 percent on average from 2006 peaks and mortgage rates touching record lows near 4-3/4 percent.

(Reporting by Lynn Adler, Editing by Chizu Nomiyama)