The New Zealand government says pension portability issues are complex and discussions to change the criteria are likely to take some time.
Wellington is being challenged by a group of New Zealanders retirees who are long-term residents in the Cook Islands.
The group claims the current rules are unfair as the Cook Islands is part of the realm of New Zealand.
Under the existing criteria, an application for superannuation has to be lodged in New Zealand by a person who has lived in the country for five years after turning 50.
The foreign ministry says the minister, Murray McCully, has on a number of occasions discussed the issue with affected colleagues.
It says there are some cost implications that the government will need to consider seriously in a difficult fiscal environment.
