Copper slipped to a three-week low on Wednesday after an inventory rise highlighted a healthy supply situation while aluminium sank to its lowest since April after data showed a rise in global output. Aluminium and some other metals were boosted earlier in the session by bargain hunting, but they resumed a downtrend or pared gains against the backdrop of the US/China trade dispute.
Copper hit a three-week low during Asian trading and was rebounding when data on London Metal Exchange inventories knocked the metal lower again in early European activity. The daily data showed on-warrant copper stocks in LME-registered warehouses - those not earmarked for delivery - jumped by 15,800 tonnes to 264,575, surging 38 percent since May 29.
Signals from the physical market also indicated the copper market was not suffering from shortages, said Oliver Nugent, commodities strategist at ING Bank in Amsterdam.
Fears of a trade war between the United States and China have battered financial markets and spurred a big liquidation in bullish speculative positions in metals in recent days.
Three-month LME copper closed down 1 percent at $6,773 a tonne, its weakest level since May 30.
China's refined copper output rose 15.5 percent from a year ago to 767,000 tonnes in May, government data showed.
Nickel and zinc, mainly used in the steel industry got some support when steel futures in China recovered after the previous session's nearly 3-percent drop. LME nickel, mainly used in stainless steel, was the biggest LME mover, ending 2.2 percent firmer at $14,975 a tonne after hitting a three-week low on Tuesday.
Nickel was also bolstered by reports that China's nickel pig iron output (NPI) in May fell to the lowest since August last year due to environmental checks, Alastair Munro at broker Marex Spectron said in a note.
The global nickel market deficit widened to 52,600 tonnes during the first four months of the year from 37,800 tonnes in the same period of 2017, data showed.
LME zinc largely used for galvanising steel, lost earlier gains and finished down 0.2 percent at $2,995 a tonne after touching $2,981, the lowest since May 4.
LME aluminium also went into the red by the close, falling 0.2 percent to $2,166, the weakest since April 10, after data showed global primary aluminium output in May rose to 5.441 million tonnes from a revised 5.303 million tonnes in April. Lead shed 0.6 percent to end at $2,401 while tin gained 1.5 percent to $20,675.