Workers at BHP Billiton’s Spence copper mine in Chile have threatened to strike in October if demands to renew collective contracts are not met.

The workers union at Spence has requested a 5.5% wage increase for the duration of the two-year collective contract along with bonuses ties to copper prices.

Union board member Francisco Aravena told Reuters that BHP’s offer did not meet the union’s expectations and was unsatisfactory as the company was witnessing high profits.

“The strike is our best tool to pressure the company. It will be legal and we are [within our] right to enforce it,” Aravena said.

Aravena is expected to vote on BHP’s final proposal later this week.

If the offer is rejected workers will then vote on strike action that will be enforced in early October.