U.S. home prices rose more slowly in September, indicating that weaker sales are preventing sharp price gains that were seen earlier this year, according to a monthly report released Tuesday. The Standard & Poor's/Case-Shiller 20-city home-price index rose 0.7 percent in September, down from a 1.3 percent gain the previous month. Compared to a year earlier, home prices jumped 13.3 percent, the fastest such gain since early 2006. Monthly price gains slowed in 19 of the 20 cities tracked by the index, which covers about half of U.S. homes. The index is not adjusted for seasonal variations, so the monthly changes partly reflect slower buying activity in the late summer and autumn.