The State Government has categorically denied union claims it plans to privatise Fremantle Port.
The Maritime Union has reached an agreement with the government over pay but negotiations over job security have stalled.
The Union wants a guarantee that jobs would be safe if all or part of the port was to be privatised.
It is now threatening an eight day strike starting on Monday and involving more than one hundred workers, which threatens to cause disruptions in the lead up to Christmas.
The union has accused the government of moving towards privatisation, but the WA transport minister Troy Buswell has ruled it out.
"That is a ridiculous claim, now the government has absolutely no plans to privatise Fremantle Port, it's a state owned port, and as far as we're concerned always will be a state owned port.
Mr Buswell says negotiations have been frustrating, and retailers and customers should not be held to ransom in the lead up to Christmas.
"They are incredibly difficult to deal with," he said.
"Our response to them is keep the port open, accept a very generous pay rise and understand very clearly the fact, and that being that Fremantle Port is not and will not be privatised."