They added that dealings remained light as traders headed into the new year and the market really had only one full-day session left to trade.
"A lot of the business looks to be end-of-the-year type, but nothing of any size. We have an early close tomorrow, so today is really it - and the phones are not ringing off the hook," one trader said.
The New York Mercantile Exchange's COMEX copper market will close early, at 12:05 pm, Friday and will be shut on Monday for the New Year's Day holiday. Trading will resume on Tuesday.
Benchmark March copper futures were down 3.30 cents at $2.0360 a lb., a penny off the lower end of its $2.0260-$2.0690 trading range.
Spot January was off 3.30 cents at $2.1610 a lb., moving between $2.1550 and $2.1925.
Volume at 10 am was estimated at a modest 3,000 lots. A sharp increase of 7,150 tonnes in inventories on the London Metal Exchange pressured the market at the open. The rise brings total stocks there to 87,750 tonnes, the highest level since October 2004.
"There is some understandable nervousness about today's copper stock increase and also about market rumours that the Codelco strike may not materialise," Edward Meir, a market analyst with Man Financial Inc, wrote.
"However, barring any official word definitely ruling out a strike, we believe that today's copper decline should be relatively modest in scope."
Contract workers at Codelco, the world's biggest copper producer, launched noisy protests on Thursday to demand a bonus due to soaring copper prices, but stopped short of a national strike.
The 28,000 workers said, however, they would organise national strikes early next week, if the state-owned company did not agree to pay them a bonus of 500,000 pesos ($972) each to reflect copper prices hitting repeated records on international markets.
In other news, Chile produced 475,107 tonnes of the red metal in November, up 0.6 percent from the same month a year ago, the official statistics institute said Thursday. Copper output in the first 11 months of 2005 totalled 4,775,794 tonnes, down 2.5 percent from the same period in 2004, the institute said.
LME three-months copper cut its losses by midsession as copper picked up anticipated support near the $4,400/$4,420 level. It was trading at $4,427.50 a tonne, off the session low at $4,415 but still down from Wednesday's kerb close of $4,483.