Workers say they are committed to winning their strike action

Staff downed tools last week at the Escondida mine, which is majority-owned by mining giant BHP Billiton.

The Chilean government has hinted for the first time that it may intervene in the dispute.

Workers have threatened to walk away from talks if bosses do not improve on an existing 3% pay increase offer.

Union officials had demanded a 13% pay rise and a bonus of 16m pesos ($29,400; �15,500).

But they have since halved their bonus demand and said they would accept a 10% salary hike.

Force majeure

Workers argue that a recent surge in global copper prices means that their pay demands can easily be afforded.

But BHP Billiton insists that the price trend is temporary and is unrelated to the mine or workers productivity.

Chilean president Michelle Bachelet said there was "negotiation under way".

"It's an issue between private parties, but undoubtedly the government, if there is room to help it reach fruition, will do it," she said.

BHP Billiton has declared "force majeure", giving it legal protection and letting it miss contracted agreements, such as delivery of copper concentrate as a result of the slump in production.

The Escondida mine, north of the capital Santiago, produces about 8% of the world's copper, and daily production has dropped by almost two-thirds because of the strike.