If Helen Clark wants to lead the United Nations, she should make her intentions clear sooner rather than later, says Prime Minister John Key.
Ms Clark, currently head of the United Nations Development Programme, has long been considered a strong contender for the job, which has never been held by a woman.
"There's no question she's an immensely credible candidate," Mr Key said on the Paul Henry programme this morning.
"It's about time in the 70-year history of the United Nations to have a woman in charge."
But there has also never been a Secretary-General from eastern Europe, which has provided six of the seven confirmed candidates for this year's vote.
However, with growing tensions in the region between superpower Russia and the West, Mr Key says Ms Clark could sneak through the middle. The permanent five members of the UN Security Council -- Russia, the US, the UK, China and France -- can veto any candidates.
"If she put her name forward, [she] could become the compromise candidate -- the one where so-and-so vetoes one person, so-and-so vetoes another, and in the end she becomes the person."
Mr Key replaced the former Labour leader as Prime Minister in 2008, but would put their political differences aside should she decide to run.
"It's no great secret her politics are different from mine -- but that doesn't mean I can't have enormous respect for her ability and her capacity to do the job. And actually she, in the United Nations context, could easily be arguably the strongest Secretary-General they've had."
But with the candidate pool already at seven, and likely to grow, Mr Key says she needs to make the call.
"Theoretically she could go later, but I think that's a fraught strategy. There are people pouring in now, and she needs to decide, am I in or am I out?"
If she's in, Mr Key says New Zealand would nominate her and give her whatever resources she needed to run a campaign.
Former Australian Prime Minister Kevin Rudd is also considering a bid, asking a number of leaders at the Nuclear Security Summit in Washington DC if they'd back his bid. But Australian Foreign Minister Julie Bishop told reporters at the weekend none had promised him their support.
Tony Abbott, another former Australian Prime Minister, had previously committed to giving Ms Clark Australia's support, if she ran.