Copper futures dropped in New York and London trading, driven by a rising dollar that sent some commodity futures brokers and traders into profit-taking mode.
Copper futures for delivery in two months slipped 10.4 cents to $3.765 per pound on the Chicago Mercantile Exchange's Globex electronic commodities exchange.
On the London Mercantile Exchange, copper futures dropped $8.50 to $377.85 per metric ton; overall, the contract has gained about 25 percent this year.
"Copper followed the currencies initially," Randy North, a trader at RBC Capital Markets in New York, told Bloomberg News. "But there appears to be a bit of profit-taking around now."
Other base metals like zinc, tin and aluminum also fell. In larger terms beyond the effects of currency, it's hard to tell how the prices of the metals will move going forward.
"There has been mixed macro data recently, so it provides little guidance as market participants ponder over the size and format of more quantitative easing in the U.S.," Andrey Kryuchenkob, an analyst at VTB Capital in London, told Bloomberg News.