Rio Tinto's long wait to get a bigger share of the copper and gold produced by Indonesia's Grasberg mine has been delayed by at least two years thanks partly to recent changes to mining laws in Indonesia.

Grasberg is one of the world's biggest producers of copper and gold, and Rio had been expected to take ownership of 40 per cent of production from the mine starting in 2021 under a long-standing agreement with US company Freeport-McMoran.