The union representing workers at Freeport McMoran Copper & Gold's giant Indonesian mine is demanding a 20-fold pay rise and could strike again if its demands are not met, a union leader said on Wednesday.

Pay talks are in their second week and come after an eight-day union workers' strike in July, which lifted global copper prices since it caused Freeport to stop production at a mine with the biggest recoverable copper reserves.

The union, which represents 8,000 members, is pushing for $30-$200 an hour pay, since it says other Freeport workers around the world get paid much more than the current $1.5-$3.5 per hour for the Grasberg mine's lowest or mid-level staff, said union official Virgo Solossa.

"We in the east are in a weak position. We are in a remote area, so it is easy for a big company to exploit us. We are operating in the same way as the mine workers in Chile and Congo. The only difference is the pay," Solossa told Reuters.

Solossa said if the firm refused to give in to workers' demands by an Aug. 17 deadline, there was a possibility of another strike.

Freeport Indonesia declined to comment.

At Chile's Escondida, the world's top copper mine, negotiations between workers and mine owner BHP Billiton also stretched into a second day on Wednesday as both sides seek an end to a two-week strike that is fanning global supply fears.

Copper prices hit record highs earlier this year, but Solossa said most Freeport workers still needed bank loans to pay for their children's education.

The regional monthly minimum wage was 1.3 million rupiah ($154) last year in Papua, a province that is one of Indonesia's most impoverished and where poor infrastructure leads to higher costs.

A Freeport source said that if the company granted the union's demands, it would boost local inflation and provoke other mine workers to stage similar strikes around a country that is the world's top exporter of tin and thermal coal.

Jakarta-based employment lawyer Ibrahim Senen said the worker demands were "illogical" and too high to be granted.