US copper futures tumbled more than 5 percent at the open on Thursday, pressured by a broad sell-off in the metals, but prices managed to climb off the lows after dollar pared morning gains, sources said. "It's just mass liquidation across the board in all the metals this morning," said one dealer.
By 10:39 am EDT (1439 GMT), copper for July delivery was down 19.40 cents, or 5.35 percent, at $3.43 a lb. on the New York Mercantile Exchange's COMEX division, after dipping to a 7-day low at $3.34.
NYMEX halted trading in copper futures for 15 minutes at 9:39 am EDT, after the benchmark July contract tumbled by its maximum 20-cent daily limit. Spot June slipped 20.65 cents, or about 5.6 percent, at $3.51, after dealing between $3.44 and $3.72.