Union leaders said they were pessimistic on Friday after failing to reach an accord with officials from Freeport-McMoRan to end an indefinite strike at the Cerro Verde mine.

Workers at the mine that produces 2 percent of the world's copper put down their tools on Sept. 29 demanding higher wages.

Talks have failed to bring the sides closer. The company says Cerro Verde is operating with 600 workers that volunteered to work during the strike.

Workers, whose contract expired on Aug. 31, want a new pact to raise their salaries 11 percent, but Cerro Verde is only offering a 3 percent raise, according to the union.

This is going really badly, we have an abysmal difference in terms of what we are asking and what the company is offering, said union leader Leoncio Amudio.

Workers from across the developing world have demanded a greater chunk of soaring mining profits brought on by high metals prices. Freeport McMoRan also faces a strike in Indonesia at Grasberg, the world's third-largest copper mine.

We held a meeting this morning but there was no agreement, said Miguel Angel Huamon, who is leading the negotiations for Peru's labor ministry in the southern region of Arequipa, near the mine.

We'll meet again on Monday at 2 p.m., both sides are participating.

In addition to negotiations in Arequipa over the contract that spurred the strike, talks are being held in Lima to resolve a dispute relating to a 2010 labor contract.

Leftist President Ollanta Humala's government has deemed the strike legal for the first time in Cerro Verde's 40-year history, enabling the union to ask the government to resolve the dispute. But authorities say they will continue to push both sides to reach an agreement.

Cerro Verde produced 312,336 tonnes of copper in 2010 in Peru, the world's No. 2 copper producer behind neighboring Chile.