FILE PHOTO: Trucks travel along a road inside Chuquicamata open pit copper mine, which is owned by Chile's state-run copper producer Codelco, near Calama city, April 1, 2011. REUTERS/Ivan Alvarado/File Photo

SANTIAGO (Reuters) - Unionized workers at Codelco’s Chuquicamata copper mine, one of the world´s largest, said late on Wednesday they would walk off the job beginning Friday after failing to reach a labor deal with Codelco, the world’s top copper producer.

Chuiquicamata unions 1, 2, and 3 voted to reject Codelco´s latest proposal in an assembly Wednesday evening, saying the deal did not meet key demands, including an adequate health care plan, fair treatment of workers and retirement benefits.

Workers “decided unanimously to initiate a walk-off beginning the first shift on Friday, June 14,” the unions said in a statement.

The state miner said it regretted the workers’ decision. The deal it had offered was the “best effort Codleco could offer while still being responsible to the country, considering the transformation that both the company and the Chuquicamata division are undergoing,” the company said in a statement.

The labor strife comes as Codelco is seeking to transform the century-old 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.

Unions 1, 2 and 3 represent nearly 3,000 workers and make up over 80% of the mine’s workforce.