U.S. home prices rose modestly in June, pushed up by strong sales and a limited supply of available properties.

The Standard & Poor's CoreLogic Case-Shiller 20-city home price index increased 5.1 percent in June compared with a year ago. That's down from a 5.3 percent annual gain in May and is the slowest year-over-year pace since last August.

Home values are still soaring in the Northwest, but have slowed to more sustainable rates elsewhere. In Northeastern cities such as New York and Washington, D.C., they are rising at roughly the rate of inflation, and in Boston, less than 5 percent.

Still, overall prices are increasing more quickly than incomes as buyers compete for the dwindling supply of available homes. That could stifle home sales in the coming months.