(REUTERS) -- Striking workers at Freeport McMoRan Copper & Gold Inc's giant Indonesian mine delayed on Saturday until next week a plan to go back to work after a three-month strike because of technical issues, a union spokesman said.

The union representing miners at the Freeport's Grasberg mine struck a pay rise deal on Wednesday and agreed to end the strike which has crippled production in the world's second biggest copper mine. It agreed to start mobilising workers to work on Saturday.

However, the union said it had yet to start transferring about 9,000 workers who had joined the strike back to the highland mine because it needed to work with management on technical issues such as which division should be taken up to the mine first, a schedule of shifts and accommodation.

Mobilising thousands of workers is not a simple matter because there are so many things that need to be put in mind to avoid any disagreements among the workers and with the management, union spokesman Juli Parorrongan told Reuters by telephone.

The workers would return to work next week, he said.

Freeport had said it was losing 2 million lb of copper and 3,000 ounces of gold in lost daily production.

Prices for copper, used in power and construction, have fallen by about 12 percent since the stoppage began on Sept. 15, mostly due to uncertainty over the European debt crisis, though supply worries have helped limit the price fall.

Management of the mine did not comment on the delay in the resumption of work. In a statement last week, it said it was expecting workers to return to work in the coming days.

A union field coordinator said workers are also waiting for a statement from Freeport's subsidiaries, which include a port operator, caterer and heavy equipment maintenance unit, to guarantee no disciplinary action would be taken against contractors who joined the strike.

engki Binur, the field coordinator, said another main consideration was security.


The mine in eastern-most Papua province is surrounded by jungle where rebels and other gunmen roam. Several workers, security officers and illegal miners have been shot dead while passing along the mine's main road in recent months.

On Saturday, a helicopter rented by Freeport with 26 passengers on board was shot at by unidentified gunmen after it took off from Tembagapura town, just below the mine, police spokesman Wachyono told Reuters by telephone text message.

Freeport Indonesia spokesman Ramdani Sirait said one passenger had sustained minor injuries and the company was cooperating with police to investigate the shooting.

Freeport said it had begun ramping up milling operations at the remote Grasberg mine, which also holds the world's largest gold reserves and produces silver, although shipments would be limited this month.

Shipments of concentrate are expected to be limited until full operations are restored, which is expected by early 2012.

The strike harmed Freeport's total production, and fourth-quarter copper sales are now expected to be 800 million lb, down from a previous target of 915 million.

For gold, Freeport now expects to sell 105,000 ounces of the precious metal in the fourth quarter, down from a previous forecast of 305,000 ounces.