U.S. home prices rose in March, with the Dallas-Fort Worth measure reaching a new high, according to the Standard & Poor’s/Case-Shiller index released Tuesday.Prices increased from the previous month in 19 of the 20 markets tracked but the gains are decelerating as fewer Americans can afford to buy, S&P/Case-Shiller said in a statement.In DFW, home prices moved up 1.2 percent from February and gained 10 percent from March of 2013, consistent with the 10 percent increase in the index in 2013. Even as existing home sales have cooled in recent months, area prices continue to climb thanks to a tight inventory of homes for sale.New York was the only market to register a slight decline in the S&P/Case Shiller report. Leading the gains was San Francisco with a 2.4 percent monthly increase, while prices in Seattle, another hub for technology firms, rose 1.9 percent. Overall, the index rose 12.4 percent in March compared to 12 months earlier. While healthy, that rate of growth has slowed from both February and January. The housing market has struggled in recent months, after notching strong growth in the first half of 2013. Rising prices and higher interest rates beginning in the middle of last year made homes less affordable for would-be buyers. Meanwhile, a limited supply of homes is available as new construction has focused increasingly on rental apartments, instead of single-family homes. And 9.7 million Americans are stuck in homes worth less than their mortgage debts, making them reluctant to sell, according to the real estate data firm Zillow.The price gains over the past 12 months were the “result of a witch’s brew,” said Stan Humphries, chief economist at Zillow. It was made possible by the lows of the housing bust that began in 2007, the historically low mortgage rates and a limited supply of homes on the market. “These influences are beginning to fade, and we’re already seeing a monthly slowdown in home prices in more recent data,” Humphries said. Ian Shepherdson, chief economist at Pantheon Macroeconomics, said the monthly gains reported by the Case-Shiller index seem excessive. “Every indicator of housing market activity and prices we know is slowing or falling outright,” Shepherdson said. The index is not adjusted for seasonal variations, so the gains can reflect the warmer weather after a harsh winter. Tampa showed the largest slowdown in annual price gains. Its growth rate went from 13.4 percent year-over-year in February to 10.7 percent in March. Las Vegas and San Francisco posted the strongest year-over-year growth. The Case-Shiller index covers roughly half of U.S. homes. The index measures prices compared with those in January 2000 and creates a three-month moving average. The March figures are the latest available. This article includes material from The Associated Press and Star-Telegram archives.