Government officials will look at various issues to make sure the system is a safe one for both countries, which continue to work to keep Covid-19 out.
Speaking to TVNZ's Breakfast, she said: "I have said that it is close - that we do expect to be in the position to open up the bubble soon."
Ardern said the initial country-to-country negotiations had turned to state-by-state discussions as the earlier process had taken too long.
"We've had 12 gatherings of our officials, between the two countries, to work on country-to-country arrangement.
"We've since said: 'Look, let's just move state by state because it's actually just taking a bit too much work, a bit too difficult to get that country-to-country arrangement'.
"Let's just operate as Australia has been operating with us. That's helping to speed this up."
One of the key things they wanted to get right before opening a two-way bubble with Australia was a system to pause or stop travel from across the Tasman if and when an outbreak there happened.
And Ardern reminded Kiwis who were over there when and if that happened that they would effectively find themselves stuck.
Australian Prime Minister Scott Morrison has continued to push the move in the past few weeks. Photo / Penny Bradfield
"Just keep in mind, if something goes wrong - if there is an outbreak, we do not have the capacity in our managed isolation for everyone who would be in Australia who'd need to come back.
"So that's one of the things we'd need to work through."
Australian Prime Minister Scott Morrison has continued to push the move in the past few weeks.
Speaking to reporters earlier this month, he said he was "happy" for New Zealand to open its borders to Australia - before giving a low key jab to the Kiwis.
"If the New Zealand Government doesn't wish Australians to visit New Zealand and spend money in Queenstown or Wellington or other parts of the country, that's a matter for them.
"But if Australians can't go to Queenstown, I'm hoping they'll go to Cairns."
Speaking on the AM Show afterwards, Ardern again reiterated there was a need to "get it right" before the borders opened completely to our Aussie cousins.
One issue brought to her attention was the potential of someone travelling from a country where Covid-19 is rife and then transiting through Australia and into New Zealand - quarantine-free.
Put to her again that many people here were calling for the transtasman bubble to open now, she said officials made decisions based on health advice, not on public petitions.
