PERU’S government branded a 10-day strike at the country’s biggest copper mine illegal on Thursday.

The strike at the Antamina mine began on November 10 and the union that includes more than half the mine’s workforce is pushing for a greater share of profits.

But a government decree leaves the Sutracomasa union three days in which to appeal or send its members 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 ominously.

Antamina offered a loan for miners not on strike and warned of wage cuts for those who did not return to work as a strike entered its 11th day.

The 1,630 unionised workers are demanding a bonus to offset shrinking proceeds from a profit-sharing agreement, Sutracomasa secretary general Jorge Juarez said.

There are 2,860 workers at the mine. Most of the unionised employees work in the mining and shipping areas.

Negotiations had failed, Mr Juarez said, adding that the bonus sought by the union was to offset an expected 40 per cent drop in workers’ share of the mine’s profits.

But Antamina said that its profit-sharing system met all legal requirements and that payouts were linked to output and global mineral prices.

The Antamina mine is owned by BHP Billiton, with a 33.75 per cent stake, Glencore Xstrata, with another 33.75 per cent, Teck Resources with 22.5 per cent and Mitsubishi with 10 per cent.