U.S. home prices rose modestly in July, pulled up by strong gains in Portland, Seattle and Denver, a private index says.

The Standard & Poor's CoreLogic Case-Shiller 20-city home price index rose 5.1 percent in July from a year earlier after increasing 5 percent in June. Prices rose 12.4 percent in Portland, 11.2 percent in Seattle and 9.4 percent in Denver.

The housing market has been helped by a strong job market and low mortgage rates.

The Commerce Department reported Monday that new home sales fell 7.6 percent in August, slowing after a 13.8 percent surge in July. The National Association of Realtors said last week that sales of existing homes slid 0.9 percent in August. A shortage of available homes has limited sales and pushed prices up.