IQUIQUE, Chile, Dec 2 (Reuters) - Chile's giant Collahuasi mine and workers are close to a deal to end a month-long strikeat the world's No.3 copper deposit but continue to wrangle over bonuses, sources close to the talks said on Thursday.
Union leaders and the company head into a fifth day of talks on Friday to defuse the strike -- at 28 days, the longest ever at a major private Chilean copper deposit.
"Tomorrow will be a crucial day. The problem here is the bonus," said one source close to the talks, who asked not to be identified because of a ban on speaking publicly about the negotiations.
Labor and management have appeared keen on a deal to end the strike, which is longer than a nearly four-week 2006 stoppage at Escondida, the world's top copper mine.
A deal will likely need to be ratified in a workers' vote.
Tensions had flared at the negotiating table following a brief clash on Wednesday between police and workers demanding local authorities force strike defectors back to the picket line.
Collahuasi has operated with limited production losses thanks to a contingency plan that kept key operations running.
Mine spokeswoman Bernardita Fernandez said on Thursday operations were normalizing satisfactorily, but did not give details on how they compared to pre-strike levels.
For weeks, Collahuasi has said operations were normal according to a contingency plan, and has delivered copper to buyers in Asia and Europe.
At least 220 full-time workers broke from the strike at Collahuasi, which extracts 3.3 percent of global mined copper, or 535,000 tonnes a year. The mine has also hired hundreds of temporary workers and around 100 new, permanent employees.
The mine, owned by Xstrata (XTA.L) and Anglo American (AAL.L), had by last week probably suffered minimal losses of about 6,000 tonnes, or about 1 percent of annual output, traders say.
Copper prices CMCU3 rose with news of a possible strike, but since have shown little sensitivity to the walkout, partly because the operator has kept supplies flowing and other factors such as the euro zone debt crisis have taken precedence.
Still, a deal at Collahuasi would clear the decks for now after a series of other labor deals were inked in November.
The next major collective-bargaining talks in Chile are not scheduled until June, when state-run copper producer Codelco negotiates a new contract with workers at the 400,000-tonnes-per-year El Teniente mine.