Single-family home prices in the United States gained in June, a closely watched survey showed on Tuesday, in what could be a sign of improvement in the housing market.


The Standard & Poor’s Case Shiller composite index of 20 metropolitan areas rose 2.3 percent on an unadjusted basis. Adjusted for seasonal variables, the rise was 0.9 percent, topping economists’ forecasts for a 0.5 percent rise, according to a Reuters poll.


Prices in the 20 cities rose 0.5 percent compared with the year before.


“We seem to be witnessing exactly what we needed for a sustained recovery — monthly increases coupled with improving annual rates of change,” David Blitzer, chairman of the index committee at Standard & Poor’s, said in a statement.


“The market may have finally turned around.”


Home prices in Atlanta fared the worst, tumbling 12.1 percent from a year ago, using seasonally adjusted numbers. Phoenix continued to bounce back from poor conditions and was up nearly 14 percent.


Although prices in June were probably helped by the traditionally strong summer buying season, the gains on both a monthly and yearly basis boded well for the housing market, Mr. Blitzer said.


The report affirmed "that the overall market is healing, albeit at a frustratingly slow pace," said Stan Humphries, chief economist at Zillow.


Mr. Humphries said he expected to see prices weaken in the latter half of the year, though the period of sustained declines are likely in the past. For the second quarter, seasonally adjusted national prices jumped 2.2 percent compared with the 1.4 percent gain that was recorded in the first quarter.