Blocking asylum seekers accepted by New Zealand from later travelling to Australia risks undermining the rights of all Kiwis, New Zealand's deputy prime minister says.
New Zealand is still offering to take 150 refugees from Nauru, but Australia is sitting on draft laws which would place a lifetime ban on resettled asylum seekers being allowed to enter Australia.
New Zealand Prime Minister Jacinda Ardern has said the on-travelling decision is Australia's to make and won't change the Kiwi offer.
"Would we want to see that kind of differentiation? No, not necessarily," she told reporters on Wednesday.
"But it is still a matter for (Australia)."
But Deputy Prime Minister Winston Peters on Wednesday evening flagged concerns the law could erode his country's citizenship.
"Statements being made by the Australian political system suggest that we will have two tiers of New Zealand citizenship, one will be what we've got now and one will be for those who have come from, in this case, Nauru," he told Sky News.
"The other thing may be, if you look down the future and ask yourself: 'Could it possibly be that this secondary standard actually gets imputed, in time by Australia, to every New Zealander?'"
Mr Peters said it was too soon to make any decisions.
"It's something that has to go through the full process in Canberra for a start, so we don't know precisely what we're dealing with."
Prime Minister Scott Morrison on Tuesday talked down the prospect, telling reporters in Canberra that resettling people in New Zealand had never been his preferred outcome and could undermine a deal struck with the United States.
Successive Australian Labor and coalition governments have rejected New Zealand's offer since it was made in 2013, fearing visa-free trans-Tasman travel entitlements would be used as a marketing tool by people smugglers.
Any intake of asylum seekers to New Zealand would be part of the country's 1000-a-year refugee quota