Shanghai copper fell 2.9 percent on Monday, tracking a 4-percent slide in London futures in the previous session, as investors waited for data on China's copper trade expected this week.
The most-active August copper contract on the Shanghai Futures Exchange fell to 62,440 yuan ($8,158) a tonne from 64,320 yuan at the close of trade on Friday.
"People are looking forward to the import numbers for May. I think they are going to come in the low side and that may panic a few people," a Shanghai dealer said.
China's copper imports in the first four months of the year hit record levels as traders shipped in metal to take advantage of a positive arbitrage in Shanghai.
The arbitrage has since moderated and refined imports are seen falling to 100,000 to 140,000 tonnes a month in the third quarter, from above 200,000 tonnes per month earlier this year.
"The big question is what will happen to the material that China doesn't import? I don't think it will find its way into exchange warehouses as there are enough people out there with the will and the money to keep it out of sight," the dealer said.
Copper for delivery in three months on the London Metal Exchange gained $30 to $7,170 a tonne, after sliding $295 on Friday. A break below $7,000 may trigger further losses with technical selling driving prices towards the low $6,000s, but the threat of a strike by workers at the world's largest copper producer, Chile's Codelco, was supportive.
Codelco pledged to take steps to improve pay and conditions for subcontracted workers, but a workers' representative dismissed the promise and said the workers would press ahead with strike plans..
"Any potential action would likely affect all of the state-owned company's mining and smelting operations," Standard Bank, London, said in a note.
Codelco produced 2.1 million tonnes of copper cathode in 2006, about 11.4 percent of the world total. Contract talks at Collahuasi, one of Chile's largest copper mines, offered further support.
Investors were disappointed by a 1,461-tonne decline in Shanghai copper stocks to 93,796 tonnes last week after expectations for a 4,000-tonne fall. Nickel gained $400, or 0.95 percent, to $42,600, following a 6-percent dip on Thursday after the LME amended its lending rules, lowering the level at which the holders of long nickel positions are required to lend the metal.