Kiwi experts and leaders, including opposition leader Judith Collins, are taking umbrage at downbeat Australian assessments of beating the infectious Delta variant.

Prime Minister Scott Morrison has led a wave of attacks on the no-tolerance policy, calling it "absurd" and likening adherents to cave-dwellers.

NSW Premier Gladys Berejiklian, her state overrun with Delta cases, said last week "no amount of government intervention or lockdown is going to get you to zero cases".

On Wednesday, federal Treasurer Josh Frydenberg added his name to the mix, following a Victorian concession that it may not be able to suppress its current Delta outbreak.

"I welcome the acknowledgement in Victoria today that eliminating the Delta variant is an impossibility. It can't be done. No other country has done it, and based on the best medical advice we have, we can't do it," he said.

The comments have not gone unnoticed across the Tasman, where many have interpreted them as attacks on New Zealand's policy.

Opposition Leader Judith Collins has called the comments "cheap shots" likely to unify New Zealanders.

"It's a pretty cheap shot to take a swipe at New Zealand when we're dealing with an extended lockdown," she said.

"I'd rather they didn't do that and I'd tell them to up their game on that one.

"Kiwis stick together when you start getting attacked from overseas."

Ms Ardern appeared unperturbed by the Australian positioning, suggesting governments on both sides of the ditch had the same policy, just different politics.

"Yes I see different leaders in Australia taking different positions. But I actually think you'd see generally that their view would be keeping those cases down while you vaccinate has to be the goal. That's certainly ours," she said.

"Delta is different. No one's denying that.

"Elimination is the best strategy for us while we're vaccinating people, and then we'll continue to look at all of the evidence going forward."

New Zealand is on day 16 of a national lockdown designed to push back against the infectious variant of COVID-19.

There are signs it is working: cases have fallen from a possible peak of 83 on Sunday, with 49 cases reported on Thursday.

Kiwi experts have dismissed the calls to abandon elimination.

University of Otago public health expert Nick Wilson said a return to zero cases was firmly in New Zealand's sights.

"I was reasonably confident from the start because we had picked this up relatively early," he said.

"The prime minister in Australia, I assume he's just highly political."

Respected COVID-19 modeler Shaun Hendy, at the University of Auckland, said he was increasingly confident NZ was on track to eliminate Delta.

"You don't want countries giving up in the face of Delta," he said.

"New Zealand is demonstrating how you can beat it and people should look at that, particularly in Australia."

Elimination remains the goal in a majority of Australian states, led by hardline premiers such as WA's Mark McGowan.

Australian Associated Press