Prime Minister John Key says he is pleased the US has accepted New Zealand's invitation to send a ship but it could be weeks before he makes a decision on whether to allow it to enter New Zealand waters.
Key said Vice President Joe Biden had accepted the invitation to send a ship to the Royal NZ Navy 75th Anniversary in November. It would be the first US military ship since New Zealand passed its anti-nuclear legislation in 1987.
"Vice President Joe Biden confirmed in our discussions today that the US has accepted the invitation and intends to have a ship represent the US Navy at this event," Key said.
"We are naturally pleased the US is taking up the invitation. It is a further demonstration of the strength of our close relationship, our friendship and our shared values."
He said the acceptance would trigger the process for his decision on whether the ship the US intended to send met the anti-nuclear legislation requirements. That law forbids any vessel carrying nuclear arms or which is nuclear powered from entering New Zealand waters.
"There is a long-standing process for considering ship visits under our nuclear free legislation. I will receive advice in due course to assist me in making a decision.
"There is no specific time frame for this process but it is likely to be a number of weeks before the advice is prepared and the Government is in a position to make any further announcement."
The US has a long-standing policy of refusing to confirm or deny whether its ships have nuclear capabilities, but Key has previously said that is not required if he is satisfied the ship meets the law. That can often be ascertained by officials from publicly available information about ships' specifications.
Key said he had signed similar declarations at least 40 times for ship visits from other countries.
Asked if there would be closer military ties as a result of the decision to send a ship Key said: "If the question is will there be step back into Anzus then the answer is no. We run and independent foreign policy. We are happy with the defence tie-up we have with the United States and others, which is we make those decision on a case by case basis of what we want to do."
"Effectively you've had this one thing sitting out there and the ice was always going to broken on that and they've chose to take the 75th anniversary celebration to do that.
"It would be very odd for us to have all of our friends and acquaintances there and sending ships to celebrate the 75th naval commemoration and not have the United States there."
Biden told reporters the United States and New Zealand had taken another major step to further friendship.
"It with great pleasure and an honour Mr Prime Minister that the United States gladly accepts the invitation to send a ship to the Royal New Zealand Navy's 75th celebration this November.
"It will be another expression of our close and co-operative relationship between our two countries that we have worked so hard together to strengthen."
Key told reporters later that he did not know whether it would be a warship or what type of ship it would be.
But he said it was something to celebrate.
"I would characterise it as a victory for the relationship between New Zealand and the United States.
"This is a way of us cementing that relationship if you like and both sides being able to celebrate that we are in such good shape. It is not a victory for one side or a defeat for the other. It is a sense that actually our relationship is more important. We have dealt with the matter. It is somewhat historic now and we are taking the next step forward."
The US will not have say whether the ship is nuclear-powered or armed.Under New Zealand's anti-nuclear law, Key has to be satisfied that it complies with New Zealand law.
Biden arrived in Auckland last night and in a speech was effusive in his comments about New Zealand and its shared history with the US, particularly around defence.
He did not mention the rift of the past, nor the hugely symbolic gesture of the US Navy's return.
New Zealand and the United States shared the same values, the same commitment to freedom and equity, and the same fierce independence, Biden said.
"You nor we never bend. We never bow. We know who we are. We mean what we say. We say it in slightly different ways but it is the same."
The US is one of 30 foreign navies invited to attend the 75th birthday celebrations of the NZ Navy.
It has been mulling the invitation for the past 18 months and the matter is understood to have gone right to the Commander in Chief, President Barack Obama.
It is not known if the visit will be a one-off or if they will become a regular feature of defence contacts.
New Zealand was suspended from the Anzus security alliance in 1986 by the United States and was subjected to reprisals for more than 20 years, almost all of which have been lifted.
New Zealand has never banned US ships. Its law requires the Prime Minister to be sure that any ship visiting is neither nuclear armed or propelled.
Other nuclear powers, Britain, France and China, have sent ships to New Zealand ports in the past.
But the US for decades argued that compromised its neither-confirm-nor-deny policy, even though its warships no longer carry nuclear weapons.
Already, however, a peace group is promising to protest against any warships attending the celebrations, including the United States.
Veteran protester Valerie Morse said Auckland Peace Action was planning a flotilla to block the warships and to protest against a defence industry conference being held at the same time. "Warships have no place in our peaceful country," she said.
Biden paid a special tribute last night to US Army Captain Matthew Ferrara, a dual citizen of the US and NZ, who was killed in Afghanistan in 2007. He was also a nephew of former Defence Minister Phil Goff.
Ferrara was awarded one of the highest military honours, the Silver Star, for valour, said Biden.
Insurgents ambushed his unit before he could receive it.
Biden said that when he laid a wreath today in Auckland at the Cenotaph with Key he would be honouring Ferrara and all those other brave men and women who made the ultimate sacrifice to defend their nations. "Because our nations have made the same promise - at the going down and in the morning we will remember. We remember. We remember the sacrifices brave New Zealanders have made.
"That's who we are. We are cut from the same cloth. We may be a hell of a lot bigger but no different."
Biden was speaking at a reception in Auckland last night hosted by Foreign Minister Murray McCully.
He is on a Pacific tour to assert the US role in the Pacific.
"We are a Pacific power," he said, echoing comments made in Australia on Tuesday. "We have always been a Pacific power. We are going nowhere. We mean what we say when we say we are rebalancing to the Pacific. This is where the action is going to be."
The energy and dynamism of the region was absolutely undeniable and it was "sparking" with incredible potential. "Whether or not we reach that potential, whether or not we continue to prosper and live in peace, in our view depends on our ability to maintain a free and fair and open and liberal international system on the seas, in the skies and with free and open commerce."
He said the US and NZ had a vested interest in ensuring continued growth, stability and economic prosperity through the region "and I think we are better equipped to do that when we stand side by side to advance our mutual interests.
"It is no longer what America can do for New Zealand; it is what we can do with New Zealand that animates how the President [Obama] and I look at this relationship and, God willing, President Clinton will look at this relationship."
The US, like New Zealand, was constantly in pursuit of a more perfect union, Biden said. The US had made a lot of mistakes, he said, "but it has always been forward".
He mentioned the work the two nations did together in the Antarctic, in the Ross Sea and at the United Nations Security Council.
There was deep history of partnership including in World War II when troops were stationed in New Zealand.
His own family had a long connection with the region.
"My mother had four brothers. Two of them fought in New Guinea. One died and one came home in very bad shape and every time my grandfather would talk about his son who was lost, and New Zealand or Australia was mentioned, he straightened up.
"Not a joke. He straightened up. It's the nature of the relationship we've had."
Biden paid tribute to the New Zealand troops training Iraqi troops in Camp Taji near Baghdad.
Labour's deputy leader Annette King says news of a United States Navy ship visit later this year is a "red letter day" for New Zealand and shows the US had accepted it's non-nuclear status.
While visiting New Zealand today, US Vice President Joe Biden formally accepted an invitation to send a warship for the Royal NZ Navy's 75th Anniversary in November.
It will be the first time the US has agreed to send a ship since New Zealand passed its non-nuclear legislation in 1987 which does not allow nuclear powered ships or those carrying nuclear weapons to enter New Zealand waters.
King said that non-nuclear status had identified New Zealand as a nation for 30 years.
"We welcome the visit after 30 years of opposition from the United States, and see it as an acceptance of our nuclear free status. This issue has become core to our national identity."
She said Labour was proud to have stood firm on New Zealand's nuclear-free status, saying National had wanted to ditch as recently as 2006 when Don Brash was leader.
"It is up to the Prime Minister to guarantee to New Zealanders that any visiting warships, from any country, are not nuclear-powered or carrying nuclear weapons."
Investigative journalist and anti-nuclear campaigner Nicky Hager said a visit by a US ship was no threat to New Zealand's nuclear free policy.
"Down through the 30 years since the policy came in, there have been many pressures to try and stop it.
"But because of changes on the US warships on their side - taking off the nuclear weapons - there is no threat to New Zealand's nuclear free policy."
Nor would any visiting ship be nuclear powered, Hager said. It was well known which vessels have nuclear propulsion.
A visit would be a clear victory for New Zealand's nuclear free stance, Hager said.
"There has been a lot of pressure for New Zealand to be the one to back down. And it's kind of a miracle that New Zealand stuck to its policy through all these years and now with an American ship coming here on our terms, it's actually the New Zealand policy that has prevailed."
Security analyst Paul Buchanan, of 36th Parallel Assessments, said a ship visit would clearly signal US acceptance of New Zealand's nuclear free policy.
"The US has many ways to deal with this. My personal favourite would be for them to send the USS Mercy, which is the hospital ship based in Pearl Harbour - that would emphasise the humanitarian aspects of Naval deployments," Buchanan told Radio New Zealand.
Whatever ship was sent, it was "the end of an era of acrimony", Buchanan said, and could mark the start of a closer military relationship.
Buchanan said that, from the US perspective, any loss of face in accepting New Zealand's nuclear free stance would be worth it to strengthen the countries' relationship, as the superpower looked to increase influence in the region.
Greenpeace NZ executive director Dr Russel Norman said a US ship visit would be a "huge victory for people power".
"New Zealanders should be immensely proud. We stood up to the mightiest military power on earth, not to mention a traditional ally. And we won."
• 1984 Labour campaigned for a nuclear-free New Zealand but to remain in the Anzus security alliance with the United States and Australia, signed in 1951. Soon after winning power, David Lange and the US confidentially negotiated for the old but nuclear-capable USS Buchanan to be invited by the NZ Government.
• 1985 In January, in Lange's absence, Geoffrey Palmer and the Labour Cabinet turned down the request.
• 1986 Despite Britain's efforts to reach a compromise, none could be found and US Secretary of State George Shultz suspended NZ from Anzus. A US presidential directive set out further reprisals against New Zealand including a ban on military exercises without a presidential waiver and limited high-level Government contact.
• 2001 NZ joins US-led war on terror in Afghanistan and in 2003 sends engineers for reconstruction work in post-invasion Iraq.
• 2002 Helen Clark is invited to the White House but US remains keen to change NZ nuclear laws.
• 2007 Clark is invited to the White House where the US, under George W. Bush, accepts that NZ anti-nuclear policy won't change. The real thaw begins.
• 2010 Thaw accelerates under Obama. The US lifts the ban on military exercises with NZ and Hillary Clinton signs the Wellington Declaration for greater co-operation.
• 2012 US troops exercise on NZ soil; the Washington Declaration on greater defence co-operation between the US and NZ is signed. In July NZ is invited to take part in US-led Rimpac maritime exercise for the first time in 30 years - although consigned to civilian parts of Honolulu harbour, not Pearl Harbour.
US lifts bans on visits by NZ vessels to its ports.
• 2014 In July NZ ships in Rimpac tie up inside Pearl Harbour.
• 2014-2016 Joint exercises and missions.
• 2016 Today US accepts invitation to send a Navy ship to NZ.
Nearly a metre of snow at Mt Hutt and fire crews rescue motorists.