Rather, the mandatory mask usage will be included in the level 1 alert level settings.
The new rules are "another line of defence" when it comes to the country's Covid-19 response plan, Ardern told reporters.
The rules can be enforced by police, according to Covid-19 Response Minister Chris Hipkins said, but the focus would be on education.
"Now is the right time to make mask use mandatory in these situations. It will provide another line of defence, is a low-cost and practical option and presents a minor inconvenience by comparison."
But, by law, people can be punished if they don't follow the new rules. The punishment will be included when the orders are drafted, Hipkins said.
Both Ardern and Hipkins were at pains to point out that it will not be up to bus drivers to enforce the rules.
"We're not expecting bus drivers to stop the bus and enforce these measures," Hipkins said.
Although the rules do not apply to people in Ubers or taxis – the drivers are required to wear a mask.
Children and young people travelling to and from school are exempt from face-covering requirements on school buses and other school transport.
Although mandatory masks on public transport are not yet at a country-wide level, Ardern still encouraged people to wear masks.
"We are asking every New Zealander to continue to play their part," Hipkins said.
He said that over the past few days – since Auckland had a Covid-19 community scare – the level of compliance has been high.
The new public health order, mandating the new mask rules, will come into force at 11.59pm on Wednesday, November 18.
"It's [a mask] also a good visual reminder that while New Zealand remains relatively free of restrictions, we're not out of the woods yet. We're at level 1, not level zero."
On the Covid case last week, Hipkins said getting into a "blame game" helps no one and everyone would struggle to retrace all their steps.
He said the Government is still looking at the risks profile when it comes to the case last week.
Auckland mayor Phil Goff said he encouraged everyone to mask up on public transport.
"Widespread wearing of masks is one way that we can reduce the chances of further community transmission of Covid-19 and avoid having to go back into lockdown," he said.
"Wearing a mask while on public transport will soon be compulsory and should be part of everyone's standard practice, alongside not going to work when you have cold or flu-like symptoms, regular handwashing, cough/sneeze etiquette and keeping track of your location.
"Please follow these rules — they will help keep yourself and others safe from Covid-19," he said.
On the meat situation - where frozen New Zealand products were said to have contained traces of Covid in China - Ardern said the Government was advised that there had been positive tests from Argentina.
New Zealand products were in the same cool-store, but the Government was not officially advised that New Zealand meat had traces of Covid-19, she said.
"I want to get to the bottom of this," she said.
"This is incredibly important to New Zealand," she said.
Ardern said Apec is important for New Zealand and the last thing the world needs right now is protectionist trade policies.
She said the RCEP agreement is important for New Zealand because it opens the country up to the world more.