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SANTIAGO, June 16 (Reuters) – Workers at Chile’s state-owned Codelco, the world’s largest copper producer, will go on strike if they do not receive a favorable answer from the company’s board of directors Friday, the union said on Thursday.

The union has insisted that Ventanas, in the central zone of the country where the smelter is located, needs $53 million worth of capsules to retain certain gases, allowing operations to continue while being environmentally compliant.

“The call of the Federation of Copper Workers is to remain united, alert and mobilized, to reach the promised NATIONAL STRIKE in case the decision that the Board of Directors of the Corporation should adopt (Friday) is not favorable to the achievement of this long-awaited higher goal,” the union said in a statement.

“We are fully aware that the announcement of guaranteeing the investments that Ventanas requires is a decision that Codelco’s Board of Directors must urgently make,” it added.

In a congressional session Wednesday, Chile Mining Minister Marcela Hernando said that the studies needed to improve the unit have already been carried out, but that the decision falls on the state company’s board of directors, which has autonomous corporate governance.

The company has not responded to the workers’ demands nor to the threat of a work stoppage.

Codelco said last week it had stopped operations at the smelter while maintenance is carried out, following a recent incident in the heavily industrial area that left dozens ill with signs of sulfur dioxide poisoning.

The mining company has denied that its operations are linked to the poisonings. (Reporting by Fabian Cambero; Writing by Kylie Madry; Editing by Chris Reese and David Evans)