SANTIAGO (Reuters) - Workers at BHP Billiton's (>> BHP Billiton plc) (>> BHP Billiton Limited) Escondida mine in Chile, the world's biggest copper mine, have voted to reject a company wage offer and go on strike, the union told Reuters in the early hours of Wednesday.

The strike is due to begin in 48 hours but the union said the company will likely request government mediation to attempt a resolution, which would delay any strike action for about another week.

The vote had been expected after union leaders last week called BHP's latest wage offer "absurd" and recommended its 2,500 workers reject it and prepare for an extended conflict.

BHP did not immediately respond to requests for comment, but has previously said that its offer was fair. Workers have been offered a $12,000 (£9,548) bonus.

In the last contract talks four years ago, when the copper price was higher, workers received a $49,000 bonus after a two-week strike.

The failure of the contract negotiations has already triggered a rise in the global price of copper on expectations of a potential stoppage at the mine.

Escondida produced 1.15 million tonnes of the metal in 2015, about 6 percent of the world's total. It is majority controlled by BHP, with Rio Tinto (>> Rio Tinto plc) (>> Rio Tinto Limited) and Japan's JECO (>> JECO CO., LTD.) also owning stakes.

(Reporting by Fabian Cambero, Writing by Rosalba O'Brien; Editing by Richard Pullin)

By Fabian Cambero