The main union at Chile's Caserones copper mine said on Sunday that 98.5% of its workers had voted to reject a final offer from mine operator Lumina Copper during mediation.
The union said in a statement that as a result of the vote, that was held following a weekend-long meeting of its members, a strike had been agreed and it would begin on Tuesday at 8 am.
It said it would first meet Lumina, which is controlled by a partnership of JX Holding and Mitsui Mining, for a final period of compulsory mediation starting on Monday at 10:30am.
Lumina's human resources vice-president Claudio Raffo said the company had offered the most competitive package it could to workers, given that it had failed to meet its production targets, and had to ensure the company and its workers had a "sustainable future".
"We hope for that reason that the union members will reconsider their decision," he said. "If however that is not the case, the company will be ready to face a mobilisation in the best way it can."
The union at Caserones voted to reject Lumina's final contract offer in late July and began compulsory government-led mediation last week. A company spokesman told Reuters a second, improved offer was made during the mediation, which the union on Sunday voted to reject.
The mine produced 122 800 t of copper in 2017, just over 2% of Chile's total annual copper output.