Benchmark March futures at the Comex division of the New York Mercantile Exchange ended the day up 2.80 cents or 1.37 percent at $2.0675 a lb., after dealing from $2.0340 and a new life-of-contract high at $2.0695.
Spot December, which expires after on Wednesday's session, set a new record for copper at $2.29 a lb., and managed to close a penny off that level at $2.28.
Back month contracts settled with gains of 2.70 to 2.80 cents. "Not a lot of action from the open. We opened at $2.0650 and had a 0.25 cent close, so a lot of the buying was done overnight," said one floor dealer. He noted that China's sale of less than 20 percent of its planned volume of 20,000 tonnes in its latest tender on December 7 may have been a reason for the buying.
"That, and China's import data over the weekend which showed imports being a bit small, which tends to make me think that there is still going to be price pressure in China, which is also supportive," he added.
China imported 1,162,106 tonnes of refined copper, up 5.7 percent from a year ago, official customs figures showed on Monday. Comex final copper volume was estimated at 7,000 lots, in step with Friday's official count at 6,967 lots.
Trading continued to be moderate as desks in the United States were thinly staffed due to end-of-the-year vacations and the Boxing Day holiday in London.
London Metal Exchange trading will resume on Wednesday. On Friday, LME THREE-MONTH copper settled $20 ups at $4,450 a tonne. Supporting the rally in prices on Tuesday was news that contract workers at Chile's Codelco, the world's largest copper producer, threatened to go on strike unless the state-owned miner agreed to pay them a bonus amid soaring world copper prices.
In other news, the Commodity Futures Trading Commission (CFTC) reported the net speculative long position in Comex copper fell to 2,221 lots as of December 20, from 4,659 contracts on December 13. The nonreportable net long position fell to 962 lots, compared with 1,136 lots net long previously.