Comex copper futures rallied to fresh 6-1/2 year highs on Thursday, as a sagging US dollar and metal supply concerns amid strong demand from China sparked frantic buying in New York and London trading, dealers said.
March copper at the Comex division of the New York Mercantile Exchange rose 4.20 cents, or 3.94 percent, to $1.1085 a lb, trading from $1.0610 to a contract peak at $1.11.
On a weekly basis, futures' reached their priciest since August 1997.
"Copper is up because nobody's wants to be short the market and people who didn't buy before during the rally also are jumping on," a New York broker at a bank said.
Fundamentals are upbeat in the market with the economic outlook improving, according to analysts, while world inventories are falling and demand from China for industrial expansion projects remains robust.
Far Eastern buying and growing fund interest in metals markets recently have pushed copper to successive 6-1/2 year highs over the last month.
Some traders said the increasing threat of a strike at a Canadian copper producer also was aggravating supply concerns.
The union at the Highland Valley mine, one of the world's biggest copper producers, was urging its members reject a contract offer from the company.
A vote is expected on the offer next on Monday and Tuesday.
Highland Valley, in south-eastern British Columbia near Kamloops, is 64 percent owned by Teck Cominco Ltd.
The low-grade high-volume mine is expected to produce around 164,000 tonnes (360 million lbs) of copper this year, accounting for about 1.2 percent of annual global production.
Additionally, brokers and traders said the copper market cued off the US dollar whose renewed fall against the euro made dollar-priced commodities more attractive to overseas buyers.
The dollar fell against the euro on thoughts the European Central Bank was comfortable with the European currency's strength. The ECB left key interest rates unchanged, which had been widely expected.
Traders said the rally in New York was ignited near the close of trading at the London Metal Exchange, where three-month copper prices finished $68 higher at $2,404 a tonne.