Helen Clark says she is "deeply honoured" to be nominated by the New Zealand Government for the role of United Nations Secretary-General.
Prime Minister John Key confirmed her nomination for the UN's top job at a press conference in Wellington this morning.
Clark, the head of the United Nations Development Programme, will announce her bid in New York this morning (NZ time).
She said in a statement: "To receive the full backing of the New Zealand Government is a great honour.
"New Zealand has a proud history of supporting the United Nations from its very beginning. We, New Zealanders, have developed our own way of getting along with one another and getting things done.
"The tradition of being tolerant, pragmatic, and fair is a central part of who we are, and I believe I would bring these attributes to the position of Secretary-General."
In a press conference at New Zealand's offices at the UN, Clark said she can offer the style of leadership that is needed to help the United Nations move ahead at a challenging time.
She said New Zealand had a history of being "pragmatic and fair".
"We need a UN which is up to the task of tackling the major challenges facing the world today" and she believed she was the leader to do that.
Clark said she was "very honouored" to receive the full backing of the New Zealand Government, and the amount of traffic coming in indicated significant support from New Zealand.
She said she intended to run an "accessible" campaign and would set out her priorities in the course of the campaign.Ms Clark gave a press conference at New Zealand's offices at the UN, including a ceremony with a conch shell and waiata.
Clark said she believes the Secretary-General's role will be an "open contest" despite the widespread belief that it is the turn of a candidate from Eastern Europe to take the role.
Kevin Rudd, former Prime Minister of Australia sent a message of support to Helen Clark on Twitter.
One of her top rivals is expected to be Irina Bokova, an Eastern European who heads Unesco. However, speaking in New York after announcing her bid for the top job at the UN Clark said nominations from all member states had been called for and she expected other nominees from outside Eastern Europe to come forward.
"I judge it to be an open contest and my hope is that member states will look at what are the challenges and who has the best skills for that job."
She believed that was her.
"It is an extremely challenging position but I'm used to that. My whole adult life has seen me progressively stepping up to leadership challenges."
She said peace and security would be a major priority for her.
The UN Charter was "visionary" when it was signed in 1945.
"But some of the challenges which the world faces today were not even envisaged in 1945." She said that was in response to World War II which was a war between nations, but there were many different conflicts to contend with including civil wars and violent extremism.
"The United Nations has many tools in its tool kit. They all need to be utilised to try to build more peaceful and inclusive societies."
"I see the United Nations needing to be proactive in the way it approaches promoting the ideals of the Charter in the 21st Century and it needs to be organisationally effective in doing that."
On reform of the Security Council which New Zealand is pushing for, she said that was up to member states of the UN but she hoped the debate on that reform would reinvigorate. There were many member states, and five Permanent Members of the Security Council.
"I hope that debate will fire up again because in principle it is desirable for the Security Council to reflect the geopolitical realities of the 21st Century and not 1945. Things have moved on."
She acknowledged the importance of the five Permanent Members, but would be responsive to all member states in looking to reconcile differences. Clark pointed to her role as Prime Minister in an MMP Parliament as giving her valuable experience in working with disparate groups, saying she had always run minority governments which required building consensus.
Clark said she had not set up any meetings for her campaign in advance, and would be leaving to visit Cairo for a pre-arranged visit later today before returning to New York on Thursday when she would make some calls prior to appearing before the General Assembly to make her pitch next week.
She said no UNDP resources would be used for her campaign, which would be funded by the New Zealand Government. She was getting ethics advice and would take leave for campaign-related duties.
She did not believe there was a conflict of interest in campaigning for the Secretary General's role while she was heading a UN organisation. She said her rival candidate Irina Bokova also headed a UN organisation, UNESCO.
"My understanding is that she, like I, will be making a very clear demarcation between respective responsibilities."
There have been growing calls for a woman to lead the UN for the first time but Clark said she was seeking the job because she believed she was best for the job.
"Obviously I'm a woman, but I've never sought election on the basis of being a woman. I've always sought election, and I've sought election many times in my life, as the best person for the job."
She said in general she liked to see women having a fair and equal chance at every leadership position from the UN to Governments and leadership in general.
Key supportive of Clark bid
Speaking to reporters at the Beehive, Mr Key said Clark was "the best person for the job".
Having served as New Zealand's Prime Minister for nine years and one of the top UN roles for seven years, she had the right mix of skills and experience, he said.
Mr Key said the UN needed a proven leader to tackle the major global challenges the world was facing.
"Coming from New Zealand, Helen Clark is well placed to bridge divisions and get results. She is the best person for the job."
The Prime Minister said Clark clearly had the most experience out of the Sec-Gen candidates, but he said there was "a lot of horse trading" in choosing the next UN leader.
Mr Key said he lobbied global leaders during a visit to Washington last week, and directly raised her candidacy with US President Barack Obama.
The New Zealand Government would spend "hundreds of thousands" in supporting her bid.
He did not get any "push back" from the US when he discussed her bid, he said.
It was difficult to choose a frontrunner, because the process was highly politicised and complicated. The public should have a "degree of confidence and a degree of realism" about Clark's chances, Mr Key said.
Mr Key said the most important obstacle was the permanent five United Nations Security Council members, the US, China, France, Russia and the UK, which hold a veto.
Clark had an advantage because she was in a relatively neutral position, he said.
"Some candidates may well attract a veto from various countries. I think that's very unlikely in the case of Helen Clark."
He had not discussed her candidacy with Russia - the mostly likely of the P5 members to veto her bid because of its reported preference for an Eastern European candidate.
Mr Key and Foreign Minister Murray McCully are thought to have approved a high-level campaign and funding to support her bid.
Clark has been the head of the United Nations Development Programme for the past seven years, overseeing a global budget of $6 billion in 170 countries.
She will be the eighth candidate to enter the contest for the Secretary-General's job.
Mr Key, who defeated her to become Prime Minister in 2008, has been unstinting in his praise of her capability, and that continued yesterday at his post-Cabinet press conference.
"I've said to anyone who has asked me that Helen Clark would be a great Secretary-General of the United Nations."
Asked if it would be hard promoting a political rival, he said they had competed when he was Leader of the Opposition and she was Prime Minister. "But there's a mature point at which you put politics to one side and you acknowledge and hopefully celebrate the skills of a New Zealander, not because of their political tendencies but because of their ability and capacity to do a job," he said.
"Personally, I think if Helen becomes the next Sec-Gen of the United Nations, New Zealanders would celebrate in the same way they celebrate Lorde for her achievement in singing and Lydia Ko in golf and so many other New Zealanders in what we do."
He would do everything he could to get her over the line, he said.
But he also said people had to be realistic about their expectations.
"Whatever happens, this is going to be a highly contested campaign and there's a lot of politics involved." He thought she could do immensely well in the job. "But I also thought, myself, that Tim Groser was the best to head the WTO [World Trade Organisation] and he didn't get that."
'She will have the whole of NZ cheering her on'
Labour leader Andrew Little said he along with every other New Zealand felt "extremely proud of Helen's decision to stand for this leading international role".
"Renowned for her steely determination and formidable capabilities, she would make an excellent Secretary-General," he said.
"I have immense trust in her judgment and values and I know she will have the whole of New Zealand cheering her on."
While he was in New York last year, he heard first hand of the esteem in which Clark was held.
"It is fitting that a New Zealander may be the first woman in this role. She is, and always has been, a trailblazer, following a long line of Kiwi women who have broken through the glass ceiling."
New Zealand First leader Winston Peters said he was pleased the National Government had followed the long tradition of supporting prominent New Zealanders on the international stage by nominating Helen Clark for the United Nations leadership role.
"The nomination of the former Prime Minister, who is now head of the UNDP, for the position of UN Secretary General fits with the spirit of promoting Kiwis, as was done with Mike Moore as director general of the World Trade Organisation and Don McKinnon as Commonwealth Secretary General.
"We wish her nomination every success."
Russia critical in nomination process
Most of the other seven candidates for the job are from Eastern Europe, which has never held the post before.
If the appointment continued to be determined by geographic rotation, then it would be considered to be Eastern Europe's turn.
But the 70-year-old UN is being pressed in some quarters to appoint its first woman head and to dispense with the geographic rotation.
Russia will be critical. It has publicly said it expects the next Secretary-General to come from Eastern Europe and it has a veto, along with the other four permanent members of the Security Council - the United States, China, Britain and France.
With the UN General Assembly scheduled to hold a candidates' forum on April 13, Clark has been under the clock to declare her hand.
Under United Nations rules, the decision is made by the General Assembly on the recommendation of the Security Council.
Clark's chances would be good if the Eastern Europe countries, including Russia, failed to unite around a candidate - or if a candidate around which they united was unacceptable to other permanent members of the Security Council.
Rudd puts transtasman contest in play
The stealth campaign by former Australian Prime Minister Kevin Rudd for the job as Secretary General was revealed by Australian Foreign Minister Julie Bishop at the weekend.
Mr Rudd has avoided any confirmation he wants the job.
But Ms Bishop told reporters in Washington DC, covering her attendance at the Nuclear Security Summit, that several leaders had mentioned Mr Rudd's interest.
"It seems that Mr Rudd has visited a number of people and expressed an interest," she said.
He had not yet formally asked the Australian Government for support.
Asked if they were talking about supporting Mr Rudd, she said: "No, they were talking about the number of potential candidates."
A transtasman contest could come into play if no consensus candidate from Eastern Europe emerged.
Mr Rudd's candidacy has raised eyebrows given his record in politics.
He was elected Prime Minister in 2007 but was ditched by his own party part way through the first term. After finally regaining the position from Julia Gillard near the end of Labor's second term, he was beaten at the polling booth by Liberal leader Tony Abbott, who has since been deposed by Malcolm Turnbull.
In order to avoid having to support a Rudd candidacy, Mr Abbott arranged for the Australian Government to privately commit in writing to supporting any Helen Clark bid, in the event she decided to declare. However, he did not consult Ms Bishop and the pledge was revealed only after Mr Turnbull had deposed Mr Abbott - much to Ms Bishop's annoyance.
Many pundits in Australia believe the Australian Government would have to support a bid by Mr Rudd, were he to formally declare and seek it. That would prevent Australia actively campaigning for Helen Clark who is considered to have a much stronger chance than Mr Rudd because of her track record, and her gender.
But some pundits have said it should support any Helen Clark bid.
Mr Rudd had a famously short fuse and in one of his tantrums, at the Copenhagen climate change conference, described the Chinese as "rat f**kers."
- additional reporting Claire Trevett, Audrey Young