Britain has been lobbied to be Helen Clark's champion in her bid to be the next Secretary-General of the United Nations.

John Key has raised the matter with British counterpart Theresa May at their meeting in New York.

It comes as the UN Security Council is due to do another straw poll on the candidates next week.

The Prime Minister said Miss Clark needs a champion among the P5.

"And we think that the United Kingdom can be that champion, so here's hoping."

John Key will address the UN General Assembly just after midday, and chairs the Security Council early tomorrow morning.

NZ Herald Political Editor Audrey Young sids the escalating situation in Syria has cast a shadow over the UN this week, and is likely to put a spotlight on the Security Council meeting tomorrow.

In today's speech, she expects him to grab the moment to underline Helen Clark's credentials for the Secretary-General role.

"It is going to be a subject that John Key is going to touch on in his speech for the UN General Assembly in a few hours time, so that will be interesting to watch him campaigning from the podium."