US copper futures fell to a six-week low early Thursday as a sharp build in London warehouse stocks and macroeconomic growth concerns pinned the industrial metal down near the bottom of its range. Copper for September delivery tumbled to an early low at $3.5810 a lb, its lowest level since June 13, on the New York Mercantile Exchange's Comex division.
By 10:23 am EDT (1423 GMT), the contract was down 6.45 cents, or 1.76 percent, at $3.5930 a lb. Technical support in September copper pegged at its 200-day moving average at around $3.53. By 9 am EDT (1300 GMT), Comex estimated volumes at 4,922 lots.