A union at Chile's Sierra Gorda copper mine, controlled by Polish mining company KGHM, could go on strike this week after rejecting the latest offer in contract negotiations, the union leader told Reuters on Monday.
The company still has until the end of Tuesday to request government mediation to help reach a deal with the union of 520 workers.
"I hope they will be ready to have an agreement because at this moment there are zero conversations," said Maykel Ocayo, president of Sierra Gorda's Union 1.
Ocayo said the sticking point was the amount designated for a signing bonus. He added that the firm had promised the workers it would request the government mediation in case the offer was not approved.
A company representative was not immediately available for comment.
Sierra Gorda's Union 2 has already accepted the terms of the new contract.
KGHM took control of Sierra Gorda in 2011 when it bought the Canadian company Quadra FNX for $2.1 billion. KGHM owns 55 percent of the mine, while Sumitomo Metal Mining owns 31.5 percent and Sumitomo Corporation has 13.5 percent.
Sierra Gorda produced 101,900 tonnes of Chile's 5.8 million-tonne total copper output last year.
(By Fabian Cambero and Cassandra Garrison; Editing by Susan Thomas)