Dec 6 (Bloomberg) --  Union and company representatives at Anglo American Plc and Xstrata Plc’s Collahuasi venture failed to reach a wage agreement in a seventh day of talks as a month- long strike at the world’s third-biggest copper mine continues.

Talks will resume tomorrow, union President Manuel Munoz told reporters as he left the negotiating room today at a hotel in Iquique, Chile.

The strike, which started Nov. 5, became the longest recorded at a major Chilean copper mine, surpassing a 26-day stoppage at BHP Billiton Ltd.’s Escondida in 2006. While the company is using non-union workers and contractors to help run the mine, prospects of an output cut helped drive copper to a record on the London Metal Exchange last month.

The company and union returned to the negotiating table Nov. 29 after individual talks with workers didn’t garner enough acceptances under Chilean law to end the strike. Chile’s Work Inspectorate issued a resolution last week for talks to resume.

Collahuasi produced 535,000 metric tons last year, or 3.5 percent of global output, according to Standard Bank Plc. Its production is only surpassed by Escondida and Freeport-McMoRan Copper & Gold Inc.’s Grasberg mine in Indonesia.

Anglo American and Xstrata each own 44 percent of Cia. Minera Dona Ines de Collahuasi SCM, the mine’s operating company. A group led by Mitsui & Co. holds the remainder.