UPDATED: New Zealand will stay at level two restrictions and Auckland's level 3 restrictions have been extended until 11.59pm on Sunday, Prime Minister Jacinda Ardern has announced.

Cabinet met today to decide when to shift alert levels and Ardern is providing an update on their decision.

The alert levels were due to be lifted at midnight on Wednesday.

Ardern says tomorrow marks 14 days since the reemergence of Covid-19 outside of quarantine facilities.

She says more than a quarter of the testing done across the country has been done in the past 13 days.

Cases have emerged over the past 13 days of cases that occurred before Auckland went into level 3, she says, and if it were not for level three, the cluster would be much larger.

While the Auckland cluster is contained it is the biggest one, says Ardern.

She says the tail will be long and there will be cases for a while to come.

When Auckland moves to level 2 at midnight on Sunday there will still be a limit on mass gatherings of 10 unless people are attending a funeral or tangihanga which are limited to 50.

Ardern says keeping New Zealand at level 2 is important because of regional travel - many people will want to enter and leave Auckland once it moves into level 2.

This comes with risk, she says.

"It's a finely balanced decision, but the right one, I believe."

Exponential growth in the cluster or cases that aren't able to be linked to the cluster would mean things would change, she says.

She says the government is sticking with its "stamp it out" strategy, and acknowledges many have found it harder this time.

"We may not have any choice about whether or not the world is in a global pandemic but we do have choices about how we deal with it."

Mandatory masks on public transport

Masks will also be mandatory from Monday when using public transport at level 2 and above.

"We continue to ask everyone on public transport or planes to wear a mask," she says. "They limit the chance for Covid-19, when it is often harder to distance yourself and trace people."

She's not worried about the availability of masks but encourages people to explore buying alternatives to single-use masks if they can afford to, or to fashion a mask from things found at home.

She says they continue to encourage the use of masks between now and Monday

The alert level 2 restrictions will be reviewed before Sunday, September 6, says Ardern.

EARLIER: Prime Minister Jacinda Ardern is set to announce Cabinet's decision on whether or not alert levels in New Zealand will be lowered.

She will speak alongside Director-General of Health Dr Ashley Bloomfield at 3pm.

The announcement follows a cabinet meeting about Auckland's level three lockdown, and level two restrictions in place across the rest of the country.

The current alert levels are scheduled to lift at midnight on Wednesday.

There are nine new cases of Covid-19 in New Zealand today.

The new cases are made up of eight confirmed cases, and one probable case.

One of the cases is imported, and the other eight have been epidemiologically linked to the Auckland cluster.