Ports of Auckland says a four day strike starting tonight will cost more than $1 million.
The strike over pay and conditions by members of the Maritime Union will close down the container terminals, affecting six ships and the flow of about 4700 containers.
Chief Executive Tony Gibson says the Ports of Auckland stake holders and customers understand the company's position.
"Essentially we want to make change, we want a step change, we want a continuous improvement programme, our customers are under pressure, cost pressure, and we have to respond accordingly but we want to do that in a collaborative style with the Maritime Union.''
Mr Gibson says striking in the busy pre-Christmas period is designed to cause as much havoc as possible and it's a tactic the union has used many times before.