London Metal Exchange (LME) metals ended mostly weaker in ranges on Wednesday, drifting in thinly traded volumes on short and technical selling and profit-taking, traders said.
"The market's recent consolidation encouraged a bit of short selling in the early rings, with nickel having some technical (selling) pressure, and there was a bit of profit-taking later in the day when the dollar firmed," a trader said.
The dollar climbed against major currencies, buoyed by reports in the United States that signalled that the world's largest economy is growing at a generally healthy pace.
A stronger dollar typically puts downward pressure on the dollar-traded LME market.
LME options declarations passed routinely on Wednesday, traders said.
However, labour disputes at various plants, mines and smelters remain firmly within scope, underpinning support for metals prices.
Union workers at Alcoa's shuttered aluminium smelter in Wenatchee, Washington, planned to vote on the company's final contract proposal on Tuesday night.
Union leaders rejected an initial offer because it demanded concessions such as higher healthcare payments.
The company also faces possible worker stoppages over outsourcing work at plants in Indiana, Texas, Iowa and Tennessee, while another strike has shut down two-thirds of production at its aluminium smelter in Becancour, Quebec, since July 7.
And south of the border, operations have just resumed at Grupo Mexico's La Caridad mine copper mine after a 17-day strike, which the government had declared illegal.
Copper closed Wednesday's rings at $2,785 a tonne from $2,807 at Tuesday's kerb close, while aluminium was $17 lower at $1,686.
Zinc and nickel also edged down, although lead pushed up $20 as nearby supply tightness kept the backwardation up around $80, while tin was unchanged.