Workers at the world's largest privately-owned copper mine have given managers another chance to increase their pay offer and avoid a strike.
Copper mining is a massive business
With a walkout due to start at the Escondida mine in Chile on Monday, staff said they wanted to avoid the strike but would not back down.
Union representatives said managers had pledged to respond by midday Friday.
Staff at the mine, which is 57.5% owned by BHP Billiton want a 13% pay rise, but have so far only been offered 3%.
The 2,000 workers are also demanding a 16m peso ($29,400; £15,500) bonus, but the mine's operators are currently only prepared to go as far as 8.1m peso, double their previous offer.
Record copper prices
Staff say they are sticking to their guns because global copper prices have hit record highs this year after a surge in demand led by China's booming economy.
Analysts said any disruption to output at Escondida, which is expected to produce 1.4 million tonnes of copper this year, may lead to copper prices rising still further on the international market.
While BHP Billiton owns almost two-thirds of the Escondida mine, fellow Anglo-Australian mining giant Rio Tinto owns 30%.
The remaining stock is held by a Japanese-led consortium, with a small stake in the hands of International Finance Corp.