US copper futures opened higher on Thursday amid some short covering, supported by a drop in LME stocks and a weaker US dollar, after relatively tame US inflation data, sources said.
However, prices turned negative as speculators liquidated their long positions at the top of the day's range amid bearish Chinese import data that seemed to weigh on market sentiment.
Copper for May delivery was trading 0.65 cent lower at $2.2440 a lb by 10:31 am EST (1531 GMT), on the New York Mercantile Exchange's COMEX division, moving from $2.2325 to $2.2680, 1.60 cents shy of yesterday's 4-1/2 week high.
Spot March was down 0.70 cent at $2.2450. The all-time record for COMEX spot copper was at $2.34 a lb, set on February 6. COMEX copper volume at 9:00 am EST was estimated at 2,000 lots.