(In last paragraph, corrects to say the two mines produced 340,000 tonnes of copper in 2017, not 160,000 tonnes)
By Fabian Cambero
SANTIAGO, July 10 (Reuters) - Workers at the Zaldivar copper mine in Chile, owned by Antofagasta and Barrick Gold Corp, voted to approve a strike on Monday after talks with the company failed, a union leader told Reuters.
While the official balloting had not been completed, union officials said the vote count so far had made the outcome certain.
"We still need the official vote for the city of Antofagasta," said union president Raul Torres, referring to a city where many of Chile's copper miners live. "But the strike is already approved."
Antofagasta, which manages labor relations at Zaldivar, declined to comment on the union vote, but said it would continue to work within the guidelines established by law.
Zaldivar's workers will not walk off immediately. Rather, there will be a government mediation period that will last at least five days before workers are legally permitted to down tools.
The potential strike comes amid a complex labor landscape in Chile, by far the world's leading copper producer. New, pro-worker labor laws have emboldened miners, while low copper prices mean contract offers are not as generous as in years past.
Earlier in the year, a strike at BHP Billiton's Escondida copper mine in Chile, the world's largest, sent prices for the red metal soaring on supply concerns.
The supervisor's union at Antofagasta's nearby Centinela mine is currently in government-mediated negotiations after voting to strike at the beginning of July.
Together, Centinela and Zaldivar produced 340,000 tonnes of copper in 2016. (Reporting by Fabian Cambero; Writing by Gram Slattery; Editing by Phil Berlowitz)