It's been a whirlwind 24 hours for New Zealand's new Prime Minister Jacinda Ardern.

She has been quizzed on "what's next" in back-to-back interviews this morning, in which she's come across as upbeat.

The wheels of change whirred into action last night with Labour and National hearing Winston Peters' decision at the same time as the same time as the rest of the country.

The Labour caucus will meet today to vote on Labour's cabinet positions.

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Ardern said told Mike Hosking on Newstalk ZB that an announcement of portfolio allocations would be just days away.

"We're very, very close. It's just finalising the details of the agreement and wordsmithing," she said.

Ardern confirmed to Hosking that she found out about her rise to Prime Minister during Peters' speech, along with the rest of New Zealand.

This was not out of line with usual practise, she said, nor was the time span of the parties' "robust" negotiation talks.

"I absolutely sensed the weight of the decision through the tone of our talks."

She said she spoke to Peters immediately after the decision was announced.

When quizzed on Three's The AM Show about whether Peters would take on the role of Deputy Prime Minister, Ardern said negotiations were ongoing.

"I understand Mr Peters and his team want to make some time on those final portfolio allocations," she said.

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"I have no idea whether Mr Peters will accept that role or not."

Solid details on policy negotiations were scarce but Ardern indicated Labour's proposed water tax could be off the table, due to NZ First's opposition to the idea.

"I'm sticking to the goal of improving our waterways but Mr Peters was very firm on that", she said.

Ardern admitted on TVNZ's Breakfast it would take time for the job title to sink in, but said she plans on being a Prime Minister for all New Zealanders - whoever they voted for.

When asked if she was nervous, Ardern replied "No, I'm excited".