Pacific nations' support for New Zealand's bid for a Security Council seat will be crucial if New Zealand is to get across the line in October, and Mr Key is expected to use the event to lobby further.
Before leaving New York, Mr Key told more than 200 diplomats at a New Zealand-hosted event that whether New Zealand won or lost its bid for a seat, there had been great advantages in running the seven-year campaign.
It had been an opportunity for New Zealand to "reach out and establish new friendships and rekindle some old ones", he said.
"Whatever the result of the election in October, it leaves New Zealand with a much better understanding of so many friends around the world from different continents, and hopefully it gives you the opportunity for you to understand our country just a little bit better."
He said New Zealand was "a small country but one that brings an independent foreign policy, is good at listening and is good at trying to find out all of the facts of a situation, a country that is not afraid to stand up for what is right and to take positions.
"They are characteristics which we can guarantee we will bring to the council if we are successful in the campaign this year."
He met former Prime Minister Helen Clark, now head of the United Nations Development Programme.
The pair discussed Iraq and both said the crisis should be addressed by a political process.
Clinton and Hadlee on Key's guest list
Legendary fast bowler Sir Richard Hadlee made an appearance for his country last night at a reception in New York to try to persuade United Nations diplomats to get New Zealand on the Security Council.
Cricketing countries at the UN were invited to another event today in the UN rose gardens to promote the Cricket World Cup next year in New Zealand and Australia.
Prime Minister John Key caught up with Sir Richard at the function after joking with the diplomats about Kiwi party culture.
"If it's like a typical New Zealand party you'll be here late into the night. There'll be some dancing and some singing taking place and hopefully not too much of it recorded on an iPhone." There was a large turnout from African countries, the Iraqi ambassador was there, and the Italian ambassador was chauffeured away in a Maserati.
Earlier Mr Key had lunch with former President Bill Clinton, who might be America's first First Man.
Clinton suggested a meeting at a French restaurant. Mr Key had Caesar salad and Mr Clinton had salmon.
They talked about Iraq and what New Zealand could do in Africa with its agricultural expertise.
Hillary Clinton was away promoting her book, Hard Choices, ahead of what is widely thought to be a prelude to her declaration to run for the US presidency.