By Nathan Gill and James Attwood

Oct. 7 (Bloomberg) — Workers at BHP Billiton Ltd.’s Spence copper mine in Chile agreed to delay a strike and extend wage negotiations to give the company time to sweeten a contract offer, a union official said.

Workers, who had planned a strike starting tomorrow, will now walk out on Oct. 13 should Melbourne-based BHP refuse to improve its latest offer, said Francisco Aravena, a spokesman for the union representing about 560 workers at Spence. BHP is the world’s biggest mining company.

“This is, more than anything, us waiting for the company to deliver a substantial offer with respect to our collective contract,” Aravena said today in a telephone interview. “The conversations we’ve had haven’t been fruitful.”

Workers rejected an offer last week, prompting BHP to improve its wage proposal Oct. 5, BHP spokesman Ruban Yogarajah said today by telephone from London.

Copper futures for December delivery fell 0.2 cent to $2.7795 a pound on the Comex division of the New York Mercantile Exchange. The price has surged 93 percent this year.