SANTIAGO, Nov 20 (Reuters) - A worker´s union at Antofagasta Minerals' Centinela copper mine in Chile is preparing to vote next week on a contract offer but says it will likely reject it, paving the way for a strike at the deposit, the union chief told Reuters on Friday.

Luis Redlich, president of the Centinela District union, said workers had set the bar high following their efforts to maintain copper output even during the height of the novel coronavirus outbreak in Chile.

He said the deal offered by the company should reflect their hard work. He said he was confident that the two would reach an agreement in government-mediated negotiations following next week´s vote.

"You get to the last offer, you vote and then there is {new} space for the conversation to reach its limits," he said.

Before then, he said, "we will have to vote to strike."

Antofagasta does not comment on its labor negotiations.

Chilean law says that once a union approves a strike, the parties then attend five days of government-mediated talks, which can be extended for an additional five days.

Centinela produced 276,600 tonnes of copper last year. (Reporting by Fabian Cambero, Writing by Dave Sherwood; editing by Grant McCool)