The union’s 205 workers run the company’s Integrated Operations Centre which manages cathode and concentrator plants in the north of the country from the Chilean capital Santiago.

Union president Jessica Orellana told Reuters that 97% of the group’s workers had voted to reject the deal. The standoff comes as the global price of copper has soared, hitting decade-long highs and providing leverage to unions looking to top up existing contracts and benefits.

Chilean law allows either party to now request a five-day government mediation period, extendable for an additional five days, ahead of any eventual strike.

BHP told Reuters in a statement it believed the two parties could still reach an agreement.

“Considering the willingness for dialogue and good faith shown throughout the entire process, the company is confident in a satisfactory agreement for both parties,” BHP said.

Escondida, the world’s largest copper deposit, produced 1.19 million tons in 2020, while Spence produced 146,700 tons.