U.S. home prices edged up nearly a full percentage point in April, Standard & Poor’s (S&P) reported Tuesday. It was the first month-to-month increase recorded by the agency in seven months.

From market reactions, the lift was seemingly unexpected, although April marked the final month for homebuyers to commit to a contract in order to take advantage of the federal tax credit, which boosted purchase activity and precluded sellers from discounting property. Now that the housing tax stimulus has expired, analysts are looking for both home sales and prices to retreat.

The S&P/Case Shiller 20-city home price index rose 0.8 percent between March and April. The 10-city composite reading was up 0.7 percent.

The annual gauges posted even healthier increases. The 20-city composite rose 3.8 percent compared to April 2009, while the 10-city was up 4.6 percent. But gains

there are tempered too, since year-ago price levels signaled the market’s trough, just barely above five-year lows.

From their peak in June/July of 2006, the 20-city composite is down 30.0 percent and the 10-city index is down 30.5 percent.

David M. Blitzer, chairman of the index committee at S&P, says the near-future pullback from the homebuyer tax credit, along with a glut of foreclosures adding to the oversupply of homes already out there will likely push home prices down further still.

“Consistent and sustained boosts to economic growth from housing may have to wait to next year,” Blitzer said.

Patrick Newport, U.S. economist for the research firm IHS Global Insight says he expects another 6 to 8 percent decline in the months ahead. He doesn’t think we’ll see the bottom in home prices until 2011.

S&P notes that most of the annual price gains in April were concentrated in California. In San Francisco, home prices are up 18 percent compared to a year ago – the largest margin within the 20-city index. In San Diego, prices rose 11.7 percent over the previous 12 months, and in Los Angeles, they’ve rebounded 7.8 percent.

The city with the biggest drop in property values over the past year is Las Vegas, down 8.5 percent. However, prices there were up 0.3 percent on a month-to-month basis.

Only two cities saw home prices fall month-over-month. In Miami, prices dipped 0.8 percent, and New York saw residential values decline 0.3 percent.