The risk of strike intensified again on Monday when unions at BHP's Cerro Colorado copper mine in Chile voted to reject the company's latest contract offer.
The union last week called on its members to reject contract proposals, saying BHP was using regulatory issues as an excuse to drive down wages with inappropriate proposals.
The strike option won 98% of the vote on Monday, the union said in a statement.
The union pointed out that ordinary employees of our union have publicly rejected the government's latest proposal, and from tomorrow, the union will continue to carry out their respective requests for compulsory mediation.
BHP said in a statement that it regretted the union's decision because its latest offer improved fixed and variable expenses and cited the potential impact of environmental regulations that could affect mine operations.
In addition, BHP Billiton added that the company will maintain an open position in dialogue in order to seek an agreement that is mutually beneficial to both sides.
Chilean law allows both parties to request five to ten days of government-led mediation to reach an agreement and avoid a strike.
The global mining company reached a record deal with Chilean workers at its sprawling Escondida mine this month, an outcome that could raise the bar for wage negotiations in Colorado and elsewhere for Chile, the world's top copper producer.
The much smaller Colorado Mountains produced about 1.2% of total copper production in South America in 2020.
