Jakarta: The Indonesian government has hit back at suggestions that tough new environmental regulations imposed on the giant Grasberg copper mine are politically motivated, or related to the partial-nationalisation of the mine.

The Grasberg mine is the world's second-largest copper mine and is located in the highlands of the restive Indonesian province of Papua. It is 90.64 per cent owned by US miner Freeport McMoran, while Rio Tinto also holds a stake.

Policemen stand guard in front of the entrance to Grasberg mine run by Freeport McMoran Copper & Gold Inc. in Timika in Indonesia's Papua province in 2009. Credit:STRINGER/INDONESIA

The Indonesian government has asked Freeport to reduce the volume of "tailings", the waste byproduct from the mining operation, disposed of in nearby rivers from 50 per cent to five per cent. The rest of the tailings are disposed of on land.

That request has drawn an angry response from Freeport, which is negotiating with Indonesia to sell down part of its stake so the government would control at least 51 per cent of the mine.