House prices got a push from the homebuyer tax credit and rose 0.8% in April -- the first month-to-month price increase in seven months, according to the Standard & Poor's/Case-Shiller house price index.

The non-adjusted 20-city HPI released Tuesday shows that prices are up 3.8% from April 2009. However, S&P index committee chairman David M. Blitzer said the increase in prices is mainly concentrated in California and gains in other markets are modest.

He is concerned the April 30 expiration of the tax credit will lead to a "near-future pullback" in the housing market.

"Consistent and sustained boosts in economic growth from housing may have to wait til next year," Blitzer said.

IHS Global Insight economist Patrick Newport said the tax credit "pumped" up home sales and it will lead to a decline in prices later this year. The Case Shiller HPI is "likely to rise for another two-three months, but then start to decline. In our view, the housing glut and foreclosures will drive the national Case-Shiller index down another 6% - 8% with prices bottoming in 2011," Newport said.

The April S&P Case Shiller 20-city HPI is down 30% from the peak in July 2006.

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