The management of New Caledonia's Vale nickel plant says it could close by the end of the year if no new owner is found.
The assessment was given just hours after the planned sale of the Brazilian-owned plant to New Century Resources of Australia failed.
The Melbourne-based company pulled out after months of negotiations, saying it could not generate a structure suitable for all shareholders.
The government of the Southern province, where the plant is located, said all efforts would be made to save the 3000 jobs at risk in order to prevent a meltdown of New Caledonia's economy.
Pro-independence parties and customary leaders opposed to the sale said the plant should go into majority ownership of New Caledonian interests.
Holding a march in Noumea today, they demanded that an ownership bid by the Northern Province in conjunction with a South Korean company be considered.
Vale put its 95 percent stake in the plant up for sale in December after running up losses in the hundreds of millions of dollars.