The car industry fears a biosecurity problem blocking imported vehicles could drag on and a solution must be found.
The Vehicle Importers Association said 10,000 -12,000 cars had been turned away from New Zealand ports because of contamination by a noxious pest called the Brown Marmorated Stink Bug.
Association chief executive David Vinsen said used imports were more vulnerable than new cars.
"It is a breach in the supply chain and that's the concern. There are sufficient vehicles unsold at the moment. We have a bit of a buffer of stock for new vehicles more than used. For used it's much more of a just-in-time situation where the vehicles come in, get processed and within a fairly short space of time, they're on yards and in showrooms for sale."
He said the ships were having to go elsewhere, mainly Australia, for fumigation before returning to New Zealand for unloading.
"We've had a number of ships turned away from New Zealand and unable to discharge their cargo of vehicles, that's the immediate issue. The real problem, the cars which are backed up awaiting shipment from Japan."
He said car exporters in Japan had been unwilling to load vehicles on ships in the first place unless they were sure they could be unloaded here.
Mr Vinsen strongly supported actions to fight serious pests, but said better prevention methods needed to be found.
He said a working group of industry and government officials was set up on Thursday to find a solution.