Copper rose in London after miners at BHP Billiton's Escondida mine, the world's biggest copper deposit, said they are prepared to extend a strike by six weeks.

Miners at Escondida in Chile, who have been on strike since Aug. 7, are ready to hold out for 30 to 60 days after lowering their wage and bonus demands on Aug. 22, Luis Troncoso Munoz, president of the mine workers' union, said yesterday in an interview in Antofagasta.

The strike will keep a "squeeze on the supply," said Andrew Ferguson, who helps oversee 170 million pounds ($322 million) at London-based New City Investment Managers Ltd. "Given the strike carries on, I think you can remain bullish."

Copper for delivery in three months on the London Metal Exchange rose $52, or 0.7 percent, to $7,662 a metric ton as of 12:07 p.m. in London. The metal has gained 74 percent this year, and traded at a record $8,800 on May 11.

The striking workers are seeking a wage increase as a rally in metals prices buoys mining profit. BHP, based in Melbourne, yesterday reported a record second-half profit of $6.1 billion.

Escondida's concentrators, which process ore for shipment to smelters, were working at half their capacity, the company said yesterday. On Aug. 18, BHP temporarily stopped production after protesters blockaded the mine. Escondida supplied 8.5 percent of global copper last year.

The strikers' latest demand is a pay increase of 8 percentage points above inflation and a bonus of 10 million pesos ($18,724). BHP's last offer was an increase of 4 percentage points above inflation, and a bonus of 9.5 million pesos for a 36-month contract.
Mine profit

Mine executives Aug. 16 said the dispute was costing owners, including BHP, London-based Rio Tinto Group and Tokyo-based Mitsubishi Corp. $16 million in profit a day.

Also on the LME, aluminium gained $7.25 to $2,490.25 a ton, lead rose $20 to $1,220, zinc advanced $36 to $3,380 and tin was unchanged at $8,500.

Nickel gained $650 to $29,400 a ton after LME-monitored nickel stockpiles dropped today, exacerbating a shortage of supply of the metal used to make stainless steel.

Stockpiles dropped 240 tons, or 3.6 percent, to 6,426 tons today, taking the drop in inventory to 82 percent this year, helped by rising steel production in countries including China. Prices of the metal for immediate delivery exceeded benchmark three-month prices by as much as $5,250 a ton as of Aug. 22, more than three times as much as on Aug. 1.

"The nickel market is likely to remain tight for some time and critically low stocks could prompt further price strength and clearly more volatility," Robin Bhar, an analyst in London at UBS AG, said in a daily report.
Nickel producer

Output has declined at nickel producers this year. A strike at Inco Ltd.'s Voisey's Bay mine in Newfoundland has curbed supply since July 28. BHP, the world's third-largest nickel producer, said production at its Yabulu mine in Australia dropped by a third in the second quarter.

The shortfall in nickel will be 30,000 tons this year, according to Toronto-based Inco, the world's second-largest producer. Stainless-steel output will rise 8.6 percent to 26.4 million tons, according to the International Stainless Steel Forum.