Prime Minister Jacinda Ardern has invited US President-elect Joe Biden to New Zealand and offered him the Government's COVID-19 expertise during a "very positive and warm" phone call. 

Ardern said in an Instagram post on Monday it was a "real pleasure" to speak with Biden over the phone for the first time, and later told reporters she offered the President-elect access to data on New Zealand's COVID-19 response. 

"Much of the call focused on the desire of our two countries to work cooperatively on a range of issues of mutual interest. We discussed COVID-19 and the President-elect spoke positively about New Zealand's response to the pandemic," Ardern said.

"The President-elect also stated that was his number one priority and I offered to him and his team access to the New Zealand team and health officials in order to share our experience and things we've learnt on our COVID-19 journey."

Ardern acknowledged that New Zealand has some "advantages", such as a natural moat around the country, making it easier to close the border. But she said the US could learn from the Government's testing, contact tracing and isolation measures. 

"I doubt that he would have said that he wanted to discuss the issue further unless that was something he wanted to do. Whether that's done by an officials' level or whether or not that's done at leader level, in my view what we can offer is the same," Ardern said. 

"The one caveat, as I've said, is we're always aware of the fact that we have natural attributes that have added to our ability to respond to COVID in the way that we have. Our border is one element of that so it has meant that we've had some natural advantage. But keep in mind we've acted on that. We've had that advantage and we've used it to positive effect. 

"But it does mean that I'm very aware that what we've done won't be able to be replicated everywhere but there are many learnings that we're willing to share."

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Ardern said Biden would like to "reinvigorate the relationship" between the US and New Zealand. But when pressed on whether Biden truly described it that way, Ardern she would need to go back and check on his wording. 

"I want to go back and check the wording there whether or not that was the precise word used but that would be my characterisation of the phone call."

Ardern said Biden spoke "very favourably" of New Zealand's response to the virus, and they also discussed climate change and trade. 

But Ardern has not yet been invited to the White House. 

"Whether or not or when a visit like that may take place is entirely a matter for the White House. Obviously everyone will be taking into account the fact that we have border closures right now so that is something I leave to the White House," she said. 

"But we did talk about the fact that we are both looking forward to the opportunity to meet face-to-face."

Ardern said Australia has already extended an invitation to Biden next year to celebrate the anniversary of ANZUS, and Ardern said it "seemed only natural" to invited him to New Zealand too. 

"I can tell you that was very warmly received by the President-elect. He spoke of his fond memories of visiting New Zealand several years ago," Ardern said. 

Biden visited New Zealand in 2016 as Vice President under the Barack Obama administration. He was the most senior US politician to do so since President Bill Clinton attended APEC in 1999. 

"He has an interest in our region, not only stemming from his visit here and the positive impact that had, but he spoke of the time that his uncle served in the war in this region and obviously that had impacted on him and his interest in making sure that the United States is present in its engagement across the globe but particularly here."

The US presidential election result was called for Biden earlier this month after he overtook incumbent Donald Trump in the 'battleground' state of Pennsylvania, giving him more than 270 Electoral College points needed for victory. 

Trump, the Republican candidate, has so far refused to concede victory to his Democrat rival. He claims the election was rigged and that there was widespread voter fraud. But his team is yet to provide evidence.

Ardern said Trump's refusal to concede was not a topic of her discussion with Biden. 

"No, look it was very much looking to the future," she said. 

"As you can imagine, I wanted to focus the time that we had on the areas where we're really keen to work together - issues like, for instance, trade... Mostly, the time was dominated by talking about the next steps in our relationship."

Ardern had already acknowledged Biden as President-elect and Kamala Harris as Vice President-elect in a statement released on November 8. 

Biden also received congratulatory messages from Canadian Prime Minister Justin Trudeau, British Prime Minister Boris Johnson, French President Emmanuel Macron and Indian Prime Minister Narendra Modi, among others. 

"As you will have seen we already have extended as a Government on behalf of New Zealand our congratulations to the President-elect so had recognised the electoral outcome and this phone call was a follow-up to that," Ardern said.

"You'll see that we are in the company of a number of countries that have done the same and so we are amongst company in that regard."

Ardern was asked if she thinks Biden will be better than Trump for New Zealand, as some pundits have suggested, because their pair are more ideologically aligned. 

"There will always be differences in the way that leaders will operate in the relationships that they may already have, and their engagement with a country that they bring, into the job," Ardern said. 

"But certainly from that first call, I detected a huge amount of enthusiasm for the relationship that we already have but the potential of that relationship too."