Ardern said stay-at-home orders would remain in force across Auckland until August 26 in a bid to prevent a mystery outbreak from becoming a fully-blown second wave.
However, a new level 4 lockdown would have "more severe" economic implications although "international experience shows that losing control of the virus would be much more damaging to the economy" than further lockdowns.
The outbreak has cast doubt on whether New Zealand's general election will go ahead as planned next month and has halted political campaigning Ardern said she would decide by Sunday on whether to delay the election, which she can by up to about two months under New Zealand law.
Mr Barnett said that discussions with Treasury over continuation of the wage subsidy and other support mechanisms to help ease cash flow, provide some certainty to employment and business continuity have been constructive, Mr Barnett said.
The resurgence prompted the government to raise the alert levels across the country.
She said the aim was to restore level 1 freedoms as quickly as possible.
The new cases reported on Friday bring the total number of active cases in New Zealand to 48, with one person in Auckland Hospital. If symptoms develop they should seek medical advice from Healthline or their GP and isolate and get tested if they develop symptoms.
But she said it was likely the outbreak had been detected early and expressed hope that it could still be held back.
The earliest case in the cluster was a worker at the Americold Coolstore in Mt Wellington who became sick on July 31.
Ms Ardern said New Zealand's new cluster did not suggest there was a need for Auckland to be placed into level four lockdown.
Director-General of Health Ashley Bloomfield said that the family has been isolated.
"I am mindful though of the extraordinary disruption to business and the anxiety that this outbreak will be causing", Ms Ardern said.
The discovery of four new cases earlier this week had ended New Zealand's 102-day run with no new transmissions. "It appears to be new to New Zealand". Among the new cases are three workers from Auckland refrigerated warehouses, which is run by US company Americold.
Members of the cluster have travelled to Rotorua, Taupo and Morrinsville.
We are now asking that all positive cases and their families who live in Auckland transfer to the local quarantine facility. Ten of the new casess have been linked to a cool store that takes imported frozen goods from overseas.
"All confirmed cases have been transferred to the quarantine facility in Auckland".