Union at Chile's Escondida mine demand changes to contract offer

(Adds contract details, union quote)

SANTIAGO, July 12 (Reuters) - The union for Chile (Stuttgart: 704599.SG - news) 's Escondida copper mine on Thursday rejected a contract offer by the company and threatened to strike unless changes were made.

The mine, controlled by BHP, is in the middle of labor negotiations after workers extended the current contract last year, following a 44-day strike that shook the global copper market and caused huge economic losses in Chile.

The offer by Escondida, the world's largest copper mine, included a signing bonus of about $23,000 and a salary readjustment linked to inflation, which was below the guild's initial demand.

"This proposal is unacceptable and if there is no substantial change, the union will be forced to vote for a strike," the union said in a statement.

Union officials said the proposed signing bonus was too low.

"We regret that the company, again resorting to bad negotiation practices, makes its offer through the media, giving an ultimatum in that the offer is only valid until July 17," the union said. (Reporting by Fabian Cambero Writing by Cassandra Garrison; Editing by Diane Craft and Richard Chang)