WASHINGTON (MarketWatch) -- In a sign that the U.S. housing market may strengthen in coming months, an index of sales contracts on previously owned U.S. homes rose 5.3% in June from the prior month, the National Association of Realtors reported Thursday. The index, which is considered a leading indicator of existing home sales, was down 12.3% from the June 2007 level. Pending home sales in June rose in all regions, with a gain of 9.3% in the South, 4.6% in the West, 3.4% in the Northeast and 1.3% in the Midwest. The May pending home sales index was revised to a decline of 4.9% from the prior estimate of a 4.7% drop.