Foreign Affairs Minister Murray McCully is warning whalers and their opponents that New Zealand will not be sending ships to the Southern Ocean this summer - so will not be at hand to help them if they get into difficulty.
Defence authorities in both New Zealand and Australia say they are unlikely to send vessels to the southern zone during the whaling season.
As a result, Mr McCully is advising protest action to be kept within the law. The minister says the New Zealand Government cannot underwrite the safety of everyone in the Ross Sea.
He says New Zealand ships would rescue anyone they could during a maritime crisis, but dangerous conditions there and the distance from New Zealand mean it would be very difficult to do so.
New Zealand-based spokesperson for Japan's whaling programme Glenn Inwood says Japan has never asked for New Zealand's assistance and the announcement will not affect its whalers.
Greenpeace says New Zealand should take responsibility within its waters or pick up its efforts to end whaling.
The environmental group says the New Zealand government has shrugged off its responsibility and must take action.
Japanese whalers are expected to head to the Ross Sea this year, which is within New Zealand's jurisdiction.