Maritime Union of New Zealand national president Phil Adams, of Dunedin, said the union was considering industrial action over KiwiRail's decision to award a $29 million contract to build 300 open-top wagons to China CNR Corporation instead of supporting New Zealand industry.
Hillside Engineering's workshops in Dunedin submitted a tender but KiwiRail chief executive Jim Quinn said it was too expensive and the workshop appeared unlikely to be able to meet the mid-2011 delivery deadline.
Mr Adams said the union would do whatever was needed and whatever was appropriate to encourage New Zealand to use its own industry.
"It's a possibility that we would consider not unloading the carriages when they arrive at New Zealand ports.
"A lot of people are saying we should do something in a couple of months. But the Maritime Union believes we should act now.
"We are trying to be proactive - to try and stop what is happening at Hillside.
"New Zealand is not supporting its own industry enough, and they are more than capable of doing the work.
"If we don't unload the containers, it would go a long way to bringing the situation to a head. It would highlight the plight of Hillside on a nationwide scale.
"If Hillside ask for our support, we'll give it."
However, the Rail and Maritime Transport Union of New Zealand - the union that represents workers at Hillside - believes it is too early to consider the option.
National president Jim Kelly, of Dunedin, said he had discussed the idea with Mr Adams, but believed there might be other ways to deal with the situation.
He said the issue of New Zealand rail stock being made overseas instead of in New Zealand was a political decision.
The issue was due to be raised within the next month at a National Affiliates Council meeting, where members of associated unions would discuss the details and a possible way forward, he said.
Last month, several Dunedin engineering firms criticised KiwiRail's decision and urged the Government to recognise Hillside's value.
They warned anything that sent New Zealand money overseas threatened jobs and undermined local manufacturing.
Otago Chamber of Commerce chief executive John Christie said that while Hillside's tender was more expensive, its value to gross domestic product could have outstripped the deficit.
However, all was not lost, he said.
A substantial number of wagons was still to be built and he believed there would be other opportunities for Hillside to get some of the work.
"We're looking at the bigger picture."
A Dunedin group consisting of local union members, politicians, council representatives and engineering businesses is about to commission a report to show how a contract awarded to Hillside would benefit the wider economy.
Mr Christie, who is chairman of the group, hoped the report would highlight the benefits to KiwiRail and the Government.
