New Caledonia's leading union umbrella group has threatened with a general strike over the feared closure of the Vale nickel plant.
Several hundred members of Usoenc joined a rally in Noumea to back calls for the sale period for the plant to be extended to six month.
Last week, the planned sale to an Australian company fell over, with Vale saying it planned to close its plant at the end of October if no buyer was found.
A closure would eliminate thousands of jobs.
Two local bidders have come forward to take over the asset but there has been no word if Vale will accept any of the offers.
The president of the Southern Province Sonia Backes told the protestors that although Vale would ultimately decide, everything would be tried to avert a shutdown.