By Fabian Cambero and Alexandra Ulmer
SANTIAGO (Reuters) - Contract workers on Thursday blocked some roads to Chile's giant Escondida mine, but a deal to end the unrest at the world's No. 1 copper mine was "imminent," a union leader said in a disruption both he and majority owner BHP Billiton said had not affected output.
The vice president of Escondida's contract workers union, Roberto Rojas, told Reuters the partial blockade could "possibly" be lifted later on Thursday if an agreement is clinched.
"The blockades continue ... We're starting to see the lights of an agreement. An agreement is imminent," Rojas said, adding production has not been hit.
Rojas said he could not provide details on the potential agreement.
"Production is unaffected" by the protest over a bonus dispute, spokesman Ruban Yogarajah of Escondida's majority owner, global miner BHP Billiton
Contract workers put their tools down late on Wednesday and blocked access roads to the mine, but unionized workers did not join the industrial action and continued working their shifts, Escondida union secretary Marcelo Tapia said earlier.
The ageing Escondida has become symptomatic of mining challenges in the world's top copper producer Chile, where the lynchpin sector was hit by a wave of labor unrest and extreme weather last year.
In 2011, Escondida's output plummeted 24.6 percent from a year earlier to 819,261 tonnes of copper, its lowest level in nearly a decade, due to sinking ore grades and a two-week strike between July 21 and August 5 last year.
Last year's strike stoked supply fears that helped push the price of copper to near four-month highs in August and led the company to declare a force majeure.
At the time, the company said the work stoppage did not significantly affect production and gave no guidance on output losses.
The mine aims to boost production to more than 1.3 million tonnes a year by 2015, or about 5 percent of the global copper market.
(Editing by Simon Gardner; editing by Jim Marshall)