ESCONDIDA, CHILE -- A workers' strike at the world's largest copper mine has pushed copper prices higher by 2% on the London Metals Exchange this week.

BHP's copper mine in Escondida, Chile, has slashed output to about 50% of capacity, the company said, following the August 6 walkout.

Workers are demanding higher pay and bonuses. Striking employees have reportedly lowered their demanded wage hike to 8% above inflation, from a previous demand for a 10% increase, plus bonuses, but are incensed over plans by the company to return $3 billion to shareholders. "Copper belongs to Chile, not to the foreigners," they reportedly shouted over the weekend after rejecting the latest contract proposal from BHP.

Copper is Chile's top export.

The slowdown is costing BHP a reported $16 million a day in lost profits. Copper prices are up more than 500% over the past four years.