Shanghai copper fell more than 3 percent on Tuesday after falls in London copper on rising inventories, while news of record production at BHP Billiton and a deal between Chilean miner Codelco and workers also weighed on prices.
The most active October copper contract on the Shanghai Futures Exchange closed down 3.36 percent or 2,360 yuan at 67,800 yuan ($8,965), while Shanghai spot copper prices ranged between 67,050 yuan and 67,300 yuan, down 1,350 yuan a tonne.
"Shanghai copper futures eased after London futures failed to extend their gains," said analyst Yang Jun at China Futures, noting that LME copper was seeking to break the $8,500 resistance level.
By 0700 GMT, copper for delivery in three months on the London Metal Exchange was down $45 at $7,985 a tonne. It touched $8,212 a tonne on electronic trading platform Select on Monday, its highest since May 9.
Stocks in LME-warehouses rose by 2,725 tonnes to 101,400 on Monday, enough for just over two days of global consumption, but still half the level seen at the end of January.
"Rising LME inventories pressured copper lower, and some industrial news also capped the gains," said an LME trader based in Shanghai. "But the market is still in an uptrend," he said, adding that copper is seeing strong support under $8,000 in London and 68,000 yuan in Shanghai.
Mining firms have been ramping up production in response to higher prices, and this was underlined when BHP Billiton on Tuesday reported a 17 percent jump in copper output in the April-June quarter.
Copper, which hit an all-time high of $8,800 in May last year, rose nearly 10 percent in July supported by falling LME stocks and strikes at suppliers in Latin America. Codelco, which supplied 11 percent of the world's copper last year, signed a deal on Monday with 14,000 subcontracted workers, but failed to reach agreement with a further 4,000 workers who have been on strike for four weeks.
Nickel for three-months delivery on the London Metal Exchange was down over 2 percent, or $700, at $32,700 a tonne, after falling nearly 5 percent on Monday.