The Government's six criteria are:

1. That our response framework for when there are cases in Australia is fit for purpose.
2. We have measures in place to effectively contact-trace travellers from Australia, should we need to.
3. All technical issues are resolved; including transitting passengers and managed isolation fees - when, for instance, passengers arrive in either Australia or New Zealand but their ultimate destination is different.
4. That we have the appropriate regulatory mechanisms in place.
5. That airports, airlines and agencies are ready.
6. That the Director-General of Health has provided an up-to-date health assessment.

"Once these criteria are met, we anticipate we will be in a position to open the bubble," Ardern said.

Cabinet chose April 6 as the date for which an announcement on the travel corridor would be made because the 15 days between now and then would allow the Government to have talks with airports and airlines, Ardern said.

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Ardern says establishing a trans-Tasman bubble is a priority for Cabinet, as it will boost tourism and business and allow for the reunion of friends and family on both sides of the Tasman.

However she said "many New Zealanders are nervous" at the potential for increased transmission of COVID-19, which has infected 123 million people worldwide, and pointed out that such an arrangement would be "highly complex".

"Officials have been considering and working through these complexities for months," she said. "Cabinet today received an update on this work."

Earlier on Monday, Ardern had tempered expectations on how quickly a travel corridor between the two nations would open up.

"No-one should expect that suddenly, at the end of today, we're going to have an opening," she told The AM Show. "I don't want to raise that expectation, but we have said it will be soon." 

The Opposition has been pushing for a travel bubble between New Zealand and Australia for months but the National Party ramped up the pressure on the Government last week, launching a petition calling for its immediate implementation. 

Ardern said on Monday the bubble is something the Government had been "working hard" on.

"We just need to make sure when we do it, we get it right," she said. "A petition isn't what makes this decision - we make it based on health advice and when we believe we've got everything in place."