London Metal Exchange (LME) copper closed nearly three percent higher on Monday as the strike at the world's largest copper mine remained unresolved.
"Everybody is keeping their eyes on Escondida, the market is a bit worried... but we really need to see copper break through $8,200 in order to see it go higher," an LME trader said.
Three months copper ended at $7,650 a tonne, up 2.7 percent and versus $7,450 on Friday.
The strike at Chile's Escondida, the world's biggest mined copper deposit, entered a third week on Monday after union workers rejected the company's latest wage offer but said they wanted to continue talks.
Workers rejected a proposal late on Sunday, accusing majority-owner BHP Billiton Ltd/Plc of fiddling with numbers in its new contract proposal that included bonuses and interest-free loans worth about $32,000 per worker.
The risks of further supply disruptions remain high with almost 20 percent of current world production having contracts up for renewal between now and the end of 2006, a Macquarie Research report said.
"If any one of these operations have problems...then prices may well spike higher", Macquarie said.
Nickel prices rose as a strike at Inco Ltd's 54,000 tonne-per-year Voisey's Bay mine in Canada continued.
Nickel closed at $28,500 against $28,000. Last week the metal rallied on the back of declining stocks, hitting a new record high of $29,200. On Monday, LME-monitored nickel stocks fell 330 tonnes to 5,826, but the amount of metal available to the market rose slightly to 1,200 tonnes from 870 on Friday.
Global consumption is around 3,600 tonnes a day.
Reflecting the tightness of the market, nickel's backwardation stood at $4,800 a tonne on Monday.
The LME intervened last week in the market by limiting daily cash premiums to $300.
Zinc closed at $3,398, against $3,260, after touching a high for the day of $3,390, up 4 percent. "Zinc looks much better fundamentally than aluminium and is being well supported at $3,250," the trader said.
The number of those holding long positions in the nearby market had begun to decrease, Sempra Metals economist John Kemp said, and highlighted the shortage of stocks. These had fallen to around 180,000 tonnes from 400,000 at the beginning of 2006.
"The zinc market looks like the next candidate for a sudden price spike," he said.
Aluminium ended at $2,480 against $2,475, finding support at $2,450, dealers said.
Tin ended at $8,450/8,500 against $8,425/8,450. Lead closed at $1,195, up from $1,185.