US MIDDAY: copper sinks

US copper futures lost nearly 4 percent of their value early Tuesday as further profit-taking losses pressured prices into sell-stop orders below which quickened the pace of the decline, traders said.
By 10:57 am EDT (1457 GMT), copper for September delivery tumbled 15.30 cents, or 3.98 percent, to $3.6960 a lb on the New York Mercantile Exchange's COMEX division, its lowest point since June 18.