"We are pushing out for another eight weeks and will re-assess."
Jacinda Ardern's government halted the trans-Tasman bubble back in July for eight weeks.
Friday's fresh eight-week extension takes the travel pause through to 19 November.
Mr Robertson said New Zealand would be "extremely unlikely" to fling open the borders in November, suggesting re-openings would rely on vaccination rates.
"What we want to do is see where we are - both countries and states within Australia ... on vaccination rates in eight weeks time," he said.
"We have a desire to get New Zealanders vaccinated and once we do that, that opens up a series of options.
"The more people we get vaccinated and the quicker we get them vaccinated, the more options open up for us."
The trans-Tasman bubble was first agreed in principle by the Australian and New Zealand governments back in May 2020.
In October, NSW became the first state to allow travellers across the Tasman Sea without quarantining.
New Zealand reciprocated six months later in April, creating the trans-Tasman bubble.
However, operating the bubble proved difficult.
Kiwi health officials paused the travel arrangement several times in response to COVID-19 outbreaks in different parts of Australia.
The bubble was also unpopular in New Zealand.
While scenes of long-awaited family reunions pulled at the heartstrings, most Kiwis feared the bubble would see the return of COVID-19 in the community.
This week, a poll conducted by Labour's pollsters showed 54 per cent of New Zealanders viewed the opening "as the wrong thing to do".
Just 29 per cent of Kiwis - and just 24 per cent of Labour voters - approved of the bubble.
Ironically, the trans-Tasman bubble saw hundreds of thousands of travellers between Australia and New Zealand without spreading coronavirus.
Instead, it was a leak from New Zealand's border regime last month that produced NZ's first major outbreak in a year.
In place of quarantine-free travel, New Zealand will open up thousands of spaces in its quarantine regime, known as MIQ, for Australian-based Kiwis to come home.
Flag carrier Air New Zealand said on Friday it will operate "a limited number of quarantine flights" across the Tasman for eager travellers.
Those travellers will need to spend two weeks in quarantine, and pay the costs as per each jurisdiction's policy.
"We understand this continues to be a very distressing time for people trying to get home," Air NZ executive Leanne Geraghty said.
"We're committed to doing everything we can to get customers back to where they need to be as safely and quickly as possible."
New Zealand's latest COVID-19 outbreak has now passed 1,000 infections.
On Friday, health officials announced 11 new cases, all in Auckland, taking the Delta outbreak past the unfortunate milestone.
On the bright side, the number of recovered Kiwis now outnumber active cases for the first time since the outbreak was identified a month ago.
Of the 1,007 to test positive for COVID-19 since 17 August, 549 have recovered and 458 remain active.
It is New Zealand's 15th consecutive day where cases have been between 10 and 35.