The main union at BHP Billiton's Escondida copper mine, the world's largest, told Reuters on Tuesday that negotiations mediated by the Chilean government with the company have failed and that workers will go on strike on Thursday.
Workers warn that a strike at the Chilean mine would nearly halt production and could be lengthy, potentially affecting global supplies of a metal used in everything from construction to telecommunications.
"The company doesn't want to change its position, so we understand that there is nothing left to negotiate ... there is nothing left to talk about, we've already talked a lot and we are definitely going on strike," said union spokesman Carlos Allendes.
The strike is planned to start at 8:00 a.m. (1100 GMT).
BHP Billiton said it could not immediately comment but expected to put out a statement later in the day.