(Adds reaction from unions to offer, details, comment from Codelco)
By Fabian Cambero
SANTIAGO, June 6 (Reuters) - Unions at Chile's Chuquicamata copper mine expressed disappointment in state-run miner Codelco's latest contract offer on Thursday but agreed to extend negotiations in hopes of averting a strike.
Codelco, the world's largest copper producer, started government-mediated talks with unions 1, 2 and 3 at Chuquicamata last week after workers rejected the company's proposal.
But the unions said they were not impressed with the company's latest offer, which was proposed late on Wednesday and included a slightly higher signing bonus.
"This new offer does not cover the totality of our aspirations," the unions said in a statement. "Therefore the Union Negotiation Commission will continue to seek points of consensus."
The latest offer included a one-time package of benefits worth about $13,700 per worker, about $300 more than in a previous offer, according to two sources with knowledge of the negotiations. No official details were available.
The talks will continue through next Thursday, the unions said.
Codelco said it was doing its best to reach a deal that takes into account business conditions, the sustainability of the mine and the legitimate expectations of workers.
Unions 1, 2 and 3 represent nearly 3,000 workers and make up over 80% of the mine's workforce.
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 and Mitra Taj; Editing by David Gregorio and Dan Grebler