Peruvian government calls strike at biggest copper mine illegal

LIMA, Nov 20 (Reuters) - Peru's government on Thursday branded a 10-day long strike at the country's biggest copper and zinc mine illegal and the operating company Antamina urged laborers to return to work.

The strike, which began on Nov. 10 and stoked concerns about global copper and zinc supplies, includes more than half the mine's workforce, according to the union that called the protest to push for a greater share of profits.

The government decree leaves the SUTRACOMASA union three days in which to appeal or send its workers back to work.

"The company appeals to those who decided to be part of this industrial action to return to their jobs to avoid further damage to their salaries," Antamina said in a statement.

The union says the strike has led to a sharp decline in output, though the company has denied output is being affected. Three days into the strike, Antamina said mineral stockpiles and contract workers were helping to keep output steady.

Union boss Jorge Juarez said the workers would meet to decide whether to apply for a legal review of the government's declaration that their walkout is illegal, a move which would allow the strike be extended for another week.

The Antamina mine, in the Peruvian highlands, is controlled by BHP Billiton Ltd and Glencore Xstrata, with each holding a 33.75 percent stake.

The other companies involved are Teck, which owns 22.5 percent and Mitsubishi Corp with 10 percent.

Antamina produces about 33 percent of Peru's copper and 23 percent of its zinc. Peru is the world's No. 3 copper producer. (Reporting by Marco Aquino and Richard Lough; Editing by Grant McCool)