The Government has officially put its weight behind Ms Clark, nominating her for Secretary-General.
Prime Minister John Key this morning confirmed long-running speculation that Ms Clark wants to replace current UN Secretary-General Ban Ki-moon when his term ends, later this year.
"There are major global challenges facing the world today and the United Nations needs a leader who can be pragmatic and effective."
At her news conference at the New Zealand Mission in New York, Ms Clark formally announced her candidacy, and following a short statement was joined on stage by others for a waiata before taking questions from international media.
Ms Clark says the nomination 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."
She said the job would be a difficult one should she get the nod.
"It is an extremely challenging position, but I'm used to that.
"At its best, the position of UN Secretary-General is about giving a voice to the world's seven billion plus people who look to the UN for hope and support and inspiration."
The possibility of being the first woman in the role wasn't a factor, she said.
"I'm seeking the position because I believe I'm the best person 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 as the best person for the job."
Asked about her ambition for the role, Ms Clark said should she walk into the office in January she'd like to see a peace process in Syria already underway.
Mr Key says Ms Clark has the right mix of skills for the job, with a "vast amount of experience" in global affairs.
The Ministry of Foreign Affairs and Trade will now work with Ms Clark on her campaign.
"As I have previously said, I will do all I can to help her secure the job," Mr Key says.
He expected there to be tough competition for the job, and New Zealand's campaign would cost the taxpayer hundreds of thousands of dollars, including staff being seconded to support Ms Clark, travel related to her candidacy and promotional material.
The total cost will depend on how long her candidacy runs.
Mr Key believes she will have a "slight advantage" with New Zealand being on the UN Security Council.
"Ultimately we've got to work one person at a time. The most important obviously is the [permanent five members] because they've got the veto, and so any one of them could veto a candidate."
Mr Key had raised Ms Clark's bid with world leaders in New York last week.
"I didn't want to put them on the spot; I was simply trying to make sure an announcement would be made. What I can tell you is we didn't get any adverse reaction."
It is believed Mr Key has been in the ears of a number of world leaders, including US President Barack Obama, UK Prime Minister David Cameron and Indian Prime Minister Narendra Modi.
Green Party co-leader Metiria Turei says the party is also backing Ms Clark for the job.
Labour leader Andrew Little is also supporting her nomination, calling her a "trailblazer" who will do the job well with her "steely determination and formidable capabilities".
"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."
Yesterday, Mr Key said the Government would back Ms Clark's bid and campaign for her should she declare her ambitions, saying he'll fight for her despite their political differences and history.
"I think there's a mature point in which you put politics aside 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," Mr Key said.
There's no official deadline for applications to be submitted for the role, but the earlier candidates confirm their intentions, the earlier they can begin lobbying world leaders.
source: data archive