Freeport-McMoRan's miners in Peru launched a hunger strike on Monday, hoping to pressure the government to resolve a labor dispute 19 days into a walkout at the Cerro Verde copper mine.
Workers at Cerro Verde, which produces 2 percent of the world's copper, pulled out of negotiations on Friday and said the labor ministry must define a wage accord. The union demands an 11 percent raise.
We've exhausted all our options and only the regional government can solve this, said union leader Leoncio Amudio.
Amudio said 15 workers were participating in the hunger strike and more could join later.
The government declared the strike legal for the first time in Cerro Verde's 40-year history, enabling workers to stay on the picket line without being fired and giving the government the option to settle the dispute.
Regional authorities had been pushing for dialogue between the company and the union, but regional labor ministry head Wilmer Mixcan told Reuters on Friday they would step in to resolve the dispute if an unmanageable situation arose.
The government has also said Freeport is committing a grave infraction by relying on volunteer staff to fill jobs vacated by strikers and ordered it to pay a fine.
But Freeport's spokesman has said the mine is operating in accordance with Peruvian law and has avoided a material impact on output.
Freeport was forced to halt production at its giant Grasberg mine in Indonesia on Monday because of security fears a month after a strike began.
Cerro Verde produced 312,336 tonnes of copper in 2010 in Peru, the world's No. 2 copper producer.