(Adds union quote, details about legal process)
SANTIAGO, June 30 (Reuters) - Workers at Anglo American Plc's El Soldado copper mine in Chile rejected the company's last contract offer, a union official said on Thursday, and could go on strike in the coming days.
Jaime Munoz, a spokesperson for two of El Soldado's unions, said Anglo American's proposal was rejected by 91 percent of workers.
Both parties have the option of seeking state mediation to avoid a walkout. If mediation is not sought, the unions said, a strike will likely begin on July 4.
"We believe that the company certainly should take up the option to converse and improve the offer a bit," said Munoz.
Anglo American could not be reached immediately for comment.
El Soldado, one of Anglo American's smallest mines, produced 35,840 tonnes of copper in 2015. (Reporting by Fabian Cambero; Writing by Gram Slattery; Editing by Chizu Nomiyama and Jeffrey Benkoe)