SANTIAGO, Sept 7 (Reuters) - Workers at BHP's sprawling Escondida copper mine in northern Chile voted Wednesday to go on strike over what they described as safety concerns, the mine's union said.

Unionized workers, who say that Escondida, the world's largest copper mine, has not responded to repeated complaints about potential safety risks, voted almost unanimously in favor of the action.

The strike will entail a partial work stoppage on Sept. 12 and 14 for 12 hours each day, followed by an indefinite work stoppage lasting until a deal with BHP is reached, the union said.

Chile's President Gabriel Boric said last month he wants to ratify an International Labor Organization convention on health and safety in mines, after two workers died on a mining construction project in July and a giant sinkhole more recently opened up near a copper mine.

In a statement the union said it contacted "Minera Escondida-BHP demanding the resolution of multiple non-compliances, infractions and sustained violations, requesting the start of talks to resolve them promptly."

Escondida said in a statement Wednesday afternoon that it has complied with all its labor and contractual obligations and called the strike "unlawful" because the law establishes "clear and peaceful" mechanisms to resolve disputes.

"Regarding the alleged unsafe conditions in the operation, Escondida BHP clarifies that in a preventive manner and in accordance with its protocols, it temporarily closed the affected areas," it said, adding that it has already reported these measures to the mining regulator Sernageomin.

Other productive areas "are operating normally," the company said.

Escondida workers in March also threatened a work stoppage amid claims of breaches in their collective contract, something the company denied. (Reporting by Fabian Cambero; Writing by Carolina Pulice; Editing by Anthony Esposito, Aurora Ellis and Richard Pullin)