"According to the President, it should be wrapped up before the end of April, valuation and all," Energy Minister Ignasius Jonan told reporters.
The government, through a state-owned company, will buy the shares in PT Freeport Indonesia at "a reasonable price," including by acquiring Rio Tinto's participating interest in the massive Grasberg mine and converting it into shares, he said.
Freeport Indonesia and Rio Tinto were not immediately available to comment.
Freeport in January said it was edging closer to a permit deal with Indonesia for Grasberg, the world's second-biggest copper mine, but the miner cautioned it had not struck any formal agreements.
There has been little sign of progress since last August, when Freeport promised to divest a 51-percent stake in Grasberg to the Indonesian government in exchange for long-term operating rights. The government currently owns a less-than-10% stake in Freeport Indonesia.
A fair price for the shares has been a key sticking point in the negotiation.