SANTIAGO, Jul 29, 2011 (Dow Jones Commodities News via Comtex) -- A now week-long strike by unionized workers at Chilean copper mine Escondida, controlled and operated by global miner BHP Billiton Ltd. (BHP, BHP.AU), continued to keep operations at the world's biggest copper mine halted, a company spokeswoman said Friday.

Unionized workers at Escondida --which represented 6.7% of global copper output and some 20% of Chile's copper production in 2010, according to state copper commission Cochilco's annual report-- put down their tools late July 21 to protest what it calls unmet contract terms.

The sole union represents 96% of the union-eligible labor force and has 2,375 members.

Due to the strike, the company declared force majeure on its copper concentrate shipments on Wednesday.

Force majeure is a contract term that allows a company to temporarily halt its commitments due to an event beyond its control.

Neither the company spokeswoman nor union representatives could comment on whether both sides were holding talks.

Escondida stands to lose some 3,000 tons of copper production every day workers keep production halted.

BHP holds a controlling 57.5% stake while Rio Tinto PLC (RIO, RIO.LN) holds 30%. The remaining 12.5% is held by a Japanese consortium led by Mitsubishi Corp. (MSBHY, 8058.TO).

Last year, the open-pit mine in northern Chile produced 1.086 million tons of copper, a 1% drop from its 2009 output.