The two cranes at Wellington's port knocked out of action by the Kaikoura earthquake may not be back working for up to six months.
CentrePort was badly damaged in the November 14 quake, with the container area hardest hit.
The port has three gantry cranes. Two container cranes, which are more than 86 metres high and weigh 720 tonnes each, were rendered inoperable by ground uplift.
In the coming weeks work would secure the cranes, however it could be four to six months before container operations could resume, chief executive Derek Nind said in a statement.
That means ships without their own cranes won't be able to load or unload at the port during that time - forcing them to use other ports.
However, the port says two "geared ships" had already visited since the quake.
CentrePort was aware of the importance of container shipping to the region and had worked hard to get ships with cranes into the port, Mr Nind said.
Work on the gantry cranes will also aim to prevent them being knocked out in the event of another quake.
CentrePort's movement of ferries, fuel, logs, cars, and cruise ships continued to operate normally, Mr Nind said.