Reuters cited Mr Leoncio Amudio union leader as saying that workers at Freeport McMoRan's mine in Peru are planning to go on strike.

In June, union workers struck at the copper mine the third largest in Peru for 11 days in an attempt to pressure the company to comply with provisions in their labor contract.

He said declining to give further details "We are planning to start a strike this Thursday.”

Cerro Verde is located in the southern region of Arequipa, where last year it produced some 273,960 tonnes of copper. A company official was not immediately available to comment.

Dozens of strikes have been held this year in Peru, one of the world's leading metals exporters, as workers and the poor demand a bigger share of a seven year economic boom.