Thousands of workers at Freeport McMoRan's giant gold and copper mine in eastern Indonesia prepared to go on a month-long strike over wages at midnight on Wednesday, a workers union said.

"The strike will start midnight involving 9,000 workers and it will last for one month," Virgo Solossa, a spokesman for the Freeport workers union told AFP.

An extra 114 armed police arrived on Wednesday in the mining area from the provincial capital of Jayapura to ensure security during the protest, police spokesman Wachyono told AFP.

In July the Freeport workers held a week-long protest which disrupted production at the mine. They decided to resume the strike due to continued disagreement with the company's management over wages and welfare.

"A series of meetings with the company's management failed to reach an agreement on salary increase," Solossa said.

The workers are paid up to $3.50 an hour compared to about $40 for other Freeport employees around the world, he said. Company spokesmen could not be reached for comment by AFP.

The Freeport mine sits on some of the world's richest gold reserves and the US company's local subsidiary is the largest single taxpayer to the Indonesian government, contributing billions of dollars a year to state coffers.

The increased police presence in the area "is to anticipate any security disruption during the protest," Wachyono said, adding that there are currently 600 paramilitary police in the mining area.

Papua, a resource-rich region on New Guinea island, has been the site of a low-level separatist insurgency since its incorporation into Indonesia in the 1960s.