SANTIAGO, June 6 (Reuters) - Chilean state-run miner Codelco, the world's largest copper producer, presented workers from three unions with a sweetened contract offer late Wednesday, hoping to avert a strike at the century-old Chuquicamata, union leaders told Reuters.
Codelco entered government mediation with the unions last week after they rejected the previous offer. The company's latest proposal includes a slightly higher signing bonus than previous offers, union officials said, though details were not immediately available.
"We are still negotiating. We have not accepted that offer," said Liliana Ugarte, head of Union 2.
The three unions represent nearly 3,000 workers and make up over 80% of the mine's workforce. Union workers will vote on the offer, which is due to expire on Monday.
A representative for Codelco was not immediately available for comment.
Codelco is seeking to transform the deposit at Chuquicamata into an underground mine. The plan is part of a 10-year, $39 billion overhaul of Codelco's key operations as it seeks to maintain output despite rapidly falling ore grades at its deposits. (Reporting by Fabian Cambero; writing by Cassandra Garrison; Editing by David Gregorio)