AREQUIPA, Peru (Dow Jones)—-Compania Minera Antamina SA, one of Peru's largest base metal producers, said Tuesday that it is planning to begin work in the first half of next year on a giant expansion that will increase the life of a mine by at least seven years.

"We're in detailed engineering at the moment," Chief Executive Ian Kilgour told reporters on the sidelines of a mining conference in the southern Andean city Arequipa. "It's progressing."

New processing mills that have already been ordered, "should be operating by the second half of 2011," he added. The project is pending shareholder approval. Kilgour didn't give a price estimate for the project, but said that the company has "a steady cash flow."

"We have a record of meeting our targets," Kilgour said.

The project will increase the Antamina complex's ore processing by 38%. The mine in Peru's central highlands is a joint venture between BHP Billiton Ltd. (BHP), which holds a 33.75% stake, Xstrata PLC (XTA.LN), with another 33.75%, Teck Resources Ltd. (TCK) with 22.5% and Mitsubishi Corp. (8058.TO) with 10%.

Antamina produced 198,111 metric tons of copper and 268,877 tons of zinc in the first seven months of the year.

The company is still negotiating a labor contract with its employees, but hopes to reach a deal by the year end, Kilgour also said. The workers' contract expired July 24.

-By Leslie Josephs; Dow Jones Newswires; 511-98853-8610; peru@dowjones.com