The ban aims to boost Indonesia's long-term returns from its mineral wealth, but officials fear a short-term cut in foreign revenue could widen the current account deficit, which has undermined investor confidence and battered the rupiah currency.
Despite having more than five years to prepare for the mining law, officials just days ahead of the ban were rushing to try to soften the potential blow of the new policies.
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"The government of Indonesia will still implement the mining law consistently. But we also want to make sure its effect won't be too troublesome and lead to the laying off of workers," said Susilo Siswoutomo, vice minister of the energy and mines ministry.
Mining companies, such as Freeport McMoRan Copper & Gold , have been ramping up shipments ahead of Sunday's deadline, uncertain whether they will be able to continue after that.
"We are still on to ship through January 11. Obviously, the only thing we will try is to maximize our shipments," said Daisy Primayanti, spokeswoman for Freeport Indonesia.
The mining ministry has approved regulations that would allow Freeport, Newmont Mining Corp and others to continue to ship copper, manganese, lead, zinc and iron ore concentrate until 2017.
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But nickel ore and bauxite exports worth more than $2 billion annually would still be banned from Sunday, while coal and tin shipments would not be affected.
"We have been preparing two trade ministerial regulations on the ore export ban -- one is about the procedure for processed and refined ore exports and the other one is about the ore export ban itself," said Bachrul Chairi, director general of foreign trade at the trade ministry.
The regulations could still be tweaked and must be approved by President Susilo Bambang Yudhoyono, who is facing one of his biggest economic policy decisions in his nearly 10 years in office.