The Green Party says warships from the United States should not be allowed into New Zealand waters, regardless of how they are powered.
The US refuses to say whether its ships are nuclear-powered, resulting in an effective ban under New Zealand's nuclear-free law.
Former Prime Minister Sir Geoffrey Palmer says there's scope for some US ships to come to this country, and discussions have already taken place.
Green Party foreign affairs spokesperson, Keith Locke, says there is no place in New Zealand for US warships, nuclear or non-nuclear, when the two countries' foreign policy differs.
Labour leader, Phil Goff, says New Zealand has always been happy to receive naval ships, but such visits are approved on the assessment that they are not nuclear.
Naval ships of countries including the United Kingdom, France and China have visited New Zealand, he says.