Prime Minister Jacinda Ardern has revealed she and former US Secretary of State Hillary Clinton discussed what it was like being a mother and a politician and Clinton gave her a Buzzy Bee, saying it was a gift she had been told every New Zealand child should have.

Ardern and Clinton met over breakfast on Monday morning ahead of Clinton's speaking event at the Spark Arena tonight.

Ardern said she would not go into the detail but it was a "good discussion" which included some domestic policy in New Zealand such as he future of work, the geo-political environment "and also being a mum in the political frame."

Although Ardern has been given many gifts for the baby, she said she did not yet have a Buzzy Bee, so it was a welcome addition.

Ardern said she did not believe it was a bad move diplomatically to meet with Clinton, given Donald Trump was President and she was yet to have a one-on-one meeting with him.

She said she would meet with Trump if he wanted to meet with her.

She said Clinton fell into the same camp as President Barack Obama who she met on his visit last month.

"When it comes to the visits of those who are not guests of Government, I make sure they are treated appropriately in the same way I did when Barack Obama visited New Zealand.

"It wasn't a formal meeting, there was therefore no media. It was a private meeting and in my view doesn't change the importance of our relationship with the US and whoever the Administrator at the time."

She said the Ministry of Foreign Affairs were aware she was meeting Clinton.

Clinton had been seen in a Parnell baby shop on Sunday leading to suspicion she was shopping for Ardern who is more than seven months pregnant. In return Ardern gave her books for her grandchildren, including Hairy Maclary.

Tickets to Clinton's speaking event at the Spark Arena tonight range from $195 for the cheap seats, to $495 for the premium seating.

Former PM Dame Jenny Shipley is moderating the event which is largely to promote Clinton's book What Happened, about the 2016 presidential elections in the US.

After eight years as Secretary of State under President Barack Obama, in 2016 Clinton was the first woman to be Presidential candidate for the Democratic Party.

She was defeated by the Republican Party's Donald Trump after an acrimonious and controversial election campaign, characterised by personal attacks.

Clinton did better than Trump in the popular vote, but the electoral college system in the US saw Trump triumph.

The campaign included the ongoing fallout from Clinton's use of private email accounts during her time as Secretary of State and questions over Russian interference in the campaign, including hacking - allegations that are under investigation now.

Clinton entered politics in her own right in 2000 when she was elected to the Senate - the first First Lady to do so. That was near the end of her husband President Bill Clinton's term from 1993 to 2001.

She had been a politically active First Lady on issues such as children's health and women's rights as well as weathering the storm around the claims about President Clinton's affairs.

She was Secretary of State under President Barack Obama, visiting New Zealand in 2010 and the Cook Islands in 2014 as part of Obama's "pivot" to the Asia-Pacific.