U.S. home prices are falling again in most major cities, including Seattle, after posting small gains over the summer and spring — the latest evidence that the troubled housing market won't recover any time soon.

The Standard & Poor's/Case-Shiller index released Tuesday showed prices dropped in September from August in 17 of the 20 cities tracked. That was the first decline after five straight months where at least half of the cities in the survey showed monthly gains.

A separate index for the July-September quarter shows prices were unchanged from the previous quarter.

Americans are reluctant to purchase a home more than two years after the recession officially ended. High unemployment and weak job growth have deterred many would-be buyers. Even the lowest mortgage rates in history haven't been enough to lift sales.

David M. Blitzer, chairman of S&P's index committee, said that while the steep price declines seen between 2007 and 2009 appear to be over, home prices are down from the same time last year and do not show signs of easing.

"Any chance for a sustained recovery will probably need a stronger economy," Blitzer said.

In the Seattle metropolitan area, which includes King, Snohomish and Pierce counties, September prices were down 1.1 percent from August, the second monthly decline after five straight months of increases. Just five other cities saw bigger monthly drops: Atlanta, San Francisco, Tampa, Chicago and Las Vegas.

Seattle-area home prices were down 6.5 percent from September 2010, according to Case-Shiller.

Prices in Atlanta, Las Vegas and Phoenix fell in September to their lowest home point since the housing crisis began four years ago. Blitzer called the new lows reached in those three cities a "bit disturbing."

Seattle's low came in February.

New York, Portland and Washington, D.C., were the only cities to show monthly price increases in September.

Seattle Times business reporter

Eric Pryne contributed

to this report.